Not My Sister

by Rosie Walker

A girl stands on the doorstep, her hands tremble and her eyes glisten with tears. My sister has finally come home after six long years.

I gasp in disbelief when I meet my younger sister’s gaze. I can’t believe I’m looking at Lydia’s sweet face again. We’d been so close as children. Then one day she didn’t come home from school, and she disappeared without a trace.

Having Lydia back at home is the best thing that’s happened in years. Only I can’t shake the feeling that something isn’t right. She doesn’t remember any of the stories I tell about our childhood, she’s even forgotten her long bouts of illness. When I ask about the day she vanished, she says she doesn’t recall what happened.

I want to be close to my sister again more than anything. But when I find a strange message hidden in her room, I begin to suspect the girl who came home isn’t my sister at all. Who is she? And what really happened to Lydia?

I’m convinced I’m living with an impostor. And I will stop at nothing to expose the truth…

An absolutely gripping and addictive psychological thriller that will keep you turning the pages until late into the night. If you love The Housemaid, Gone Girl or The Other Daughter, you’ll adore Not My Sister.

Readers love Rosie
‘Had me in a hold from the first page… I devoured it in less than 24 hours! Full of twists and turns… Loved it!’ NetGalley reviewer ⭐️⭐️⭐️⭐️⭐️

‘From the moment I picked this book up, I was hooked… I even stayed up late reading… I loved it!… My favourite… The ending was one WOW!’ Arcreviews_by_m ⭐️⭐️⭐️⭐️⭐️

‘Wowsers… Just wowsers! I really was blown away! I absolutely did not see that twist coming.’ Jsybookworm ⭐️⭐️⭐️⭐️⭐️

‘Addictive. I finished it in one day because I just couldn’t put it down.’ B for bookreview ⭐️⭐️⭐️⭐️⭐️

‘Comes at you with both barrels and knocks you out of your shoes!’ Goodreads reviewer ⭐️⭐️⭐️⭐️⭐️

‘Oh my god!… Absolutely thrilling! Full of twists and turns. My jaw was hanging open.’ Jessicasbookbiz ⭐️⭐️⭐️⭐️⭐️

Genres: Psychological Thriller

367 pages, Paperback

First published March 4, 2026

About the author

Rosie Walker is a novelist who lives in Edinburgh with her husband, daughter, and dog. She has published four novels: 'Secrets of a Serial Killer', 'The House Fire', 'The Baby Monitor' and 'My Husband's Ex'.

Her next book, 'The Bride's Secret', is coming in 2025.

Rosie has a Masters in Creative Writing from the University of Edinburgh and an undergraduate degree in Psychology from Lancaster University.

Reviews

[Kelsey Nicole · Rating 4 out of 5]

4.5 ⭐️

I absolutely loved this. It was so twisty! Every time I thought we’d hit the big reveal, something even bigger happened and completely blew my mind. The story flowed really well and kept me hooked the whole way through. The characters were messy and flawed in the best way, which made everything feel more real. I loved Annabel from the very start and was always rooting for her — I really felt for her. Such a gripping read, I couldn’t put it down and loved every minute of it. The only reason it didn’t get the full 5 stars for me was because I wish we had a bit more at the end and learned more about what happened afterwards.

I can’t wait to rave about this when it’s out. I think thriller lovers are gonna eat this up!!!

Thank you bookouture & NetGalley for the early arc copy!!

[Mikayla Larlee · Rating 4 out of 5]

Not My Sister is dark, emotional, and pretty intense. The first half was a little slow and frustrating for me, but once the big reveal hit, I was completely hooked. The pacing picked up, the tension ramped way up, and the twists really landed. I also appreciated how respectfully the mental health themes were handled. Overall, a gripping and surprisingly emotional read.

Thank you NetGalley for the ARC

[Leona · Rating 4 out of 5]

Not My Sister is a twisty and at times unsettling domestic thriller. I must admit it took me a few chapters to get it this one as I found it quite slow paced. But looking back this actually was what made the story interesting, that slow burn building up to lots of tense moments. I found all the characters, (apart from Mac the dog) to be quite unlikeable. Usually in a thriller like this I can suss out fairly early on what is going on or at least have some idea. With this book I was completely barking up the wrong tree in my assumptions as to what was happening. A tense and clever read that was filled with suspense and intrigue.

[Lupita_333 · Rating 3 out of 5]

3.5 stars

Predictable story from the beginning but still super well written and drawn out.

Unrealistic in so many aspects.

Oblivious characters. I wanted so badly to be able to scream at certain characters to just call the cops and run already. There were so many obvious things that it’s shocking how they weren’t put to pieces together. So frustrating but in a good way!

Twisted and malicious character who made me fear for the other characters. I got chills when I realized the extent of their evil.

Thank you NetGalley for the ARC in exchange for an honest review.

[Kayleigh Ann · Rating 4 out of 5]

ARC from NetGalley 📖

🌟 🌟 🌟 🌟

• Loads of twists
• Never knew which characters to trust
• 100% recommend for thriller fans

Will definitely be reading more by Rosie Walker👻

[Janna (Bibliophile Mom) · Rating 4 out of 5]

Not My Sister is a dark, gripping, and emotional story about two sisters. One who mysteriously disappeared six years ago, and the other who was left behind to navigate life with their mother and estranged father. I genuinely enjoyed this book, although I’ll be honest: the first half almost threw me off. Wendy’s naivety (the mum) was hard to ignore, especially when Annabel kept voicing her doubts about Lydia’s sudden reappearance after so many years. Annabel herself also felt a little overworked as a character early on, almost as if she was trying too hard to convince the reader of her perspective.

But once I reached the halfway point, everything shifted. The major revelation hit me, and from that moment I was completely hooked. The pacing tightened, the tension escalated beautifully, and the author delivered the twists with precision. I also appreciated how thoughtfully the mental health themes were taken into the narrative. These were handled with sensitivity and respect, adding depth without feeling exploitative. Every character carried their own flaws, traumas, and emotional baggage, which made the story feel raw, genuine, and surprisingly moving.

What I enjoyed:
• The alternating first‑person narration that kept the story dynamic
• The sensitive and realistic portrayal of mental health struggles
• A shocking twist that genuinely elevated the entire reading experience

What didn’t sit right:
• One character’s naivety that made me flinch more than once
• Another character’s desperation that occasionally felt forced or exaggerated
• Dark themes that may be triggering or uncomfortable for some readers

Ratings Breakdown:
• Setting: 3⭐️
• Characters: 3⭐️
• Writing: 4⭐️
• Message: 4⭐️
• Overall: 4⭐️

Overall, I highly recommend this twisty, emotionally charged thriller. I honestly thought I’d end up disappointed, but once the story found its rhythm, I was fully invested right up to the final page. Each character is wrestling with their own pain and history, and that messy emotional landscape fuels the chaos in a compelling way. Huge thanks to NetGalley, Bookouture, and author Rosie Walker for the advance copy.

~JaNnA~

[Els · Rating 4 out of 5]

When your younger sister leaves for school one day and then disappears, your world is turned upside down. Every day you hope she will be found. Together with your mother, you put up posters and go out searching. She tries to keep people aware through the internet and encourages them to stay alert. As if that weren’t bad enough, there are two other important factors that keep the worry alive.

Until one day, your sister suddenly appears on the doorstep. Six years have passed by then.

It goes without saying that she has changed, and it’s understandable that she first wants some time to rest and recover.

Days go by, and the suspicion that this young woman might not be your sister at all grows stronger and stronger.

So it becomes time to find out what exactly happened on that tragic day.

I have to admit that along the way I noticed certain clues in the book that led me to draw conclusions which, surprisingly enough, later turned out to be correct. That didn’t bother me at all.

On the contrary—it can actually be quite nice to figure something out once in a while.

The only downside I could mention is the somewhat slow pace, at least for me. It does pick up later on, which made it more enjoyable to read and easier to get swept away by the story.

All in all, a good story with a few shocking revelations. 4 stars.

Thank you.

[Tashie_LeeReads · Rating 4 out of 5]

Overall ⭐️⭐️⭐️⭐️/5


This is one of those books that quietly pulled me in before completely flipping everything I thought I understood. Going into it, I’ll admit I wasn’t immediately hooked. The beginning felt a little slow and draggy. But in hindsight, that careful build-up is exactly what makes the payoff so crazy.

Every time I felt confident about what was happening, another twist happened and threw me for a loop. Rosie masterfully plays with perception, making you question not only the characters but also your own instincts as a reader and I love when that happens.

What truly stood out about this book is its ability to keep me guessing. The twists and turns weren't just surprising, they genuinely disoriented me in the best way, leaving me wondering whether I ever really understood what was going on in the first place.

It’s the kind of book that made me want to go back and reread earlier chapters just to catch the clues I missed.

I can't wait to read more by this author :)

[Tiffany Taylor · Rating 4 out of 5]

Thrilling, gripping and FULL of twists! Just when you think you’ve sussed it Rosie throws another spanner in the works… IN THE BEST WAY! I felt fully immersed and didn’t want to put the book down! There were moments of frustration, moments of sadness and WTF moments!

I was so convinced I’d sussed it and I did figure certain things out BUT the way it was written made you go down all sorts of paths which added a real mysterious feel to it.

So so good! Perfect for readers who love a thriller page turner with dark psychological themes

[Craig and Phil · Rating 4 out of 5]

Thank you Bookouture for a copy on Netgalley in exchange for an honest review.
Not My Sister by Rosie Walker is another winner by this author.
A tension, gripping and twisty read.
A domestic thriller that will keep you flipping the pages and that’s full of suspense.

[Kelly (aka jsybookworm) · Rating 5 out of 5]

Another brilliant 5 star read from the very talented Rosie Walker. I was gripped and on tenterhooks throughout the whole story and loved every minute of it. Definitely deserves a 5 star rating!

When a knock at the door interrupts Wendy's day she never imagines who it will be. On opening the door, she comes face to face with a young girl and suddenly something jars inside her, it's Lydia! Lydia, her youngest daughter, who suddenly went missing six years earlier on her way to school. Wendy is overwhelmed with happiness; her daughter has come back to her, and she's determined to shower her with love. However, Annabel, Lydia’s older sister is more suspicious than happy about Lydia’s return, something feels “off” to her, especially as Lydia says she has amnesia and can’t remember what happened to her or where she has been. Then there’s the biggest red flag to Annabel, Lydia’s refusal to speak to the police and admit she has been found. Wendy is just ecstatic to have her daughter back and eager to protect her at all costs and so cautions Annabel from asking probing questions. Nevertheless, Annabel is undeterred, she is desperate for the truth but at what cost might all of Annabel’s questioning come at…. is she risking alienating both her mother and long lost younger sister, maybe risking harm to herself or possibly even risking driving a very vulnerable, shaken and fearful Lydia away?!

Well only my second book by Rosie Walker and another 5 star read! I absolutely loved this story, and I also loved the multiple POV’s from Wendy and Annabel. One character really frustrated me, and I felt that with every chapter that passed I disliked them a little bit more, however despite gradually liking them less and less, I definitely did not see the twist that came, which was great writing. The second smaller twist a little later, I had sort of figured out by the time it came, but I think that’s more from my reading of lots of psychological thrillers then it being obvious- but I also liked how it rounded the whole story off and made a lot of prior preconceptions wrong- I apologise that this is a little cryptic but I don’t want to give anything away.

All in all, another fabulous read from Rosie Walker and I highly recommend this one, any fans of the psychological thriller genre will not be disappointed. I gasped (out loud), I was gripped and I was desperate to read “just one more chapter”- well done Rosie Walker, another brilliant read! I am so excited to see what you write next!

Thank you to NetGalley, Rosie Walker and Bookouture for my advanced reading copy. Out now.

[Robin Loves Reading · Rating 4 out of 5]

Rosie Walker weaves a compelling and cleverly layered tale in Not My Sister. ;/i> At the heart of the novel is Annabel’s unwavering belief that the woman claiming to be her sister Lydia - who suddenly reappears after six years - is not who she says she is.

Annabel and Lydia shared a deeply complicated childhood. Lydia was often sick, which meant she received the majority of their mother’s attention. Annabel, meanwhile, was frequently treated as an afterthought, largely because of her own struggles with mental illness and often erratic behavior. These dynamics shaped their relationship in profound ways, making Lydia’s return far from the joyful reunion their mother hopes for.

Six years have passed since Annabel last saw Lydia, and while their mother, Wendy, welcomes her daughter home with open arms, Annabel remains unconvinced. The story unfolds through alternating perspectives, revealing what feels like three distinct narratives. Annabel’s voice carries an air of unreliability that threads through the novel, while Wendy’s perspective reflects the relief and hope of a mother who believes her missing daughter has finally come home. Lydia’s version of events is mostly untold, but still rather intriguing. Clearly there are noticeable holes in her story from the very beginning (and yes, there’s Mac). Walker crafts Lydia’s narrative carefully, maintaining a steady tension as Annabel refuses to believe that this woman is truly her sister.

As much as I enjoyed the story, there were aspects of Wendy’s behavior that didn’t quite ring true for me. For instance, it seemed odd that she wouldn’t notify the police as soon as Lydia appeared on her doorstep, especially considering how involved they had been during the original disappearance. Annabel’s reluctance to involve the authorities also raised some questions. Still, given that this is a psychological thriller, that delay does help sustain the tension and allows Annabel’s growing doubt and unease to drive the drama.

Naturally, the central question looms large: Is this really Lydia? And if not, what could possibly be the motive behind such a deception? As the story unfolds, the twists and turns continue to build. While many of them genuinely shocking. I’ll admit that a few pieces fell into place for me fairly early on. Walker does an excellent job of continually planting seeds of doubt, keeping the suspense alive while the reader waits for the inevitable final reveal.

Many thanks to Bookouture and to NetGalley for this ARC for review. This is my honest opinion.

[Barbara Schultz · Rating 4 out of 5]

Title: Not My Sister
Author: Rosie Walker
Publisher: Bookouture
Genre: Psychological Thriller
Pub Date: March 4, 2026
My Rating: 4.3 Stars
Pages: 367

This story is about sisters- Lydia and Annabel.
Lydia mysteriously disappeared when she was thirteen; leaving her nineteen year old sister Annabel and their mother Wendy shattered.

Story starts six years later, when Lydia suddenly appears at the front door. Wendy assumes she is one of Annabel’s friends. However, she announces she is Lydia and has come home. Wendy doesn’t recognize her based on the age progression done by the Missing Person’s Department but does recognize a mole on her jawline.
However when Annabel comes home she has doubts - even their dog Max a miniature Schnauzer doesn’t recognize her. Mac and Lydia were once inseparable. Additionally Lydia doesn’t remember what happened plus doesn’t remember any of the stories Annabel shares about their childhood or the long illness they both had it appears all her memories are lost.

Lydia’s lack of memory is bothering Wendy so she decides to talk about her mother and her childhood. She tells Lydia about how awful it was when she was twelve and lost her twin brother Mariusz. He drowned and it tore apart the family.
This, of course, is new to Lydia.

Annabel grows increasingly convinced that this girl is not her sister.
Who is she? And what really happened to Lydia?

This is only my second Rosie Walker and I look forward to reading another.
When I read Ex-Girlfriend my comment was
The Big Reveal was a surprise!! I went into this without any expectations and it was great!!

Which is how I feel about this story.

I was curious about the Ms. Walker’s ' motivation and she tells us in “A Letter from Rosie Walker”
First she tells us that writing this was a rollercoaster; in fact the final story is very different from her original idea.
Her inspiration was based on a true story of Nicholas Barclay
- I don’t want to give too much away so if interested, I suggest you read it!

to thank NetGalley and Bookouture for this early eGalley.
Publishing Release Date scheduled for March 4, 2026.

[Amie Derricott · Rating 3 out of 5]

Wendy and her eldest daughter Annabel have always had a tenuous relationship, but even more so since her youngest daughter Lydia went missing six years ago. Things only get worse when suddenly, Lydia knocks on the door. Of course Wendy is overjoyed at her return, especially considering she seems to be in perfect health after most of her childhood was spent fighting off various ailments. Annabel is more cautious. She starts to suspect something isnt right when Lydia can’t remember any of their shared childhood memories and Lydia’s beloved dog Mac starts growling at her. Desperate to reconnect with her lost sister, Annabel becomes more and more convinced that the girl in their house is an imposter and so she begins investigating who this girl really is and what happened to her sister.
To begin with, this very much reminded me of the book The Wrong Daughter by Dandy Smith, so I anticipated that I was going to love it. Told from both Wendy and Annabels perspective we get a look at the thoughts and motivations of each of them, however so much time is spent on their internal debates and thoughts that it seems like the story really struggles to move forward. A lot of Wendy’s POV is very repetitive too, with exactly the same things being expressed in multiple chapters. I did like Annabels side of the story and I think I would have enjoyed this way more if the whole thing was told from her perspective. Considering that most of the book felt like a bit of a slog to get through, the ending was the complete opposite and felt massively rushed, everything suddenly happening and concluding in about 3 chapters. It also left me with an awful lot of unanswered questions and things that had been mentioned a couple of times never got explained as to why they were important. I contemplated a DNF, but Annabels chapters definitely saved it for me and kept me reading to find out how it was going to conclude.

[Leanne · Rating 4 out of 5]

Not My Sister is one of those thrillers that grabs you from the very first page and refuses to let go. The premise alone is deliciously unsettling—a missing sister returns after six years, but nothing about her feels quite right—and the tension only builds from there.

The story is told with a wonderfully claustrophobic sense of doubt. You can feel the narrator’s hope and heartbreak tangled together as she tries to reconnect with Lydia, only to be met with blank memories, strange behaviour, and a growing sense that the girl standing in front of her might not be who she claims to be. That creeping unease is handled so well; every chapter adds just enough suspicion to keep you turning pages.

What really works is the emotional core. This isn’t just a mystery—it’s a story about grief, longing, and the desperate need to believe in a miracle even when the truth is whispering otherwise. The hidden message discovery is a great turning point, and from there the book becomes a full‑on race to uncover what really happened the day Lydia vanished.

Fans of The Housemaid, Gone Girl, and The Other Daughter will feel right at home with the twists, the unreliable edges, and the way the story constantly shifts beneath your feet. It’s fast, addictive, and perfect for a one‑sitting read.

A gripping, eerie, and emotionally charged thriller that delivers exactly what psychological‑suspense fans crave.

My thanks to Rosie Walker, the publisher and netgalley for the ARC

[Julie Connor · Rating 4 out of 5]

Not My Sister was a gripping read that drew me in straight away. The pacing is good from the outset, and as the story unfolds, Rosie Walker pulls you along in a direction that feels completely natural and believable. Just when you start to feel settled, there’s a subtle sense of unease threaded through the narrative that keeps you second guessing what you think you know, making it very hard to put down.

I particularly enjoyed how the tension builds steadily throughout the book. Clues are revealed at just the right moments, encouraging you to form theories, only for the story to gently steer you elsewhere. It’s the kind of thriller that keeps your mind working alongside the plot, which made the reading experience especially engaging.

The ending was completely unexpected. The twists were clever, surprising, and genuinely satisfying. Everything came together smoothly, wrapping up the story in a way that was both impactful and well thought out.

Overall, this was an engaging, twisty thriller and a very enjoyable read. I’d happily recommend it to fans of psychological suspense who enjoy being kept on their toes right through to the final pages.

Thank you to NetGalley and the publisher for providing an advance copy in exchange for an honest review.

[Heidi Lynn’s BookReviews · Rating 3 out of 5]

First, I want to thank Rosie Walker, Bookouture and NetGalley for this book so I may bring you this review.

WOW!!! I can’t imagine having my sister who I am close with disappear without a trace for 6 years just to show up all disheveled out of the blue!
My mom and I would be so excited for the reunion and glad to have her home!! However, in Not My Sister by Rosie Walker you get that vibe right away that this book won't end well.

Let me be blunt right from the start I didn’t care for Lydia! She rubbed me the wrong way! A few things in particular like when she was younger she was incredibly sick however she has no recollection of that. The weird thing is she is perfectly healthy now. Lydia used to wear a back brace due to her scoliosis (I suffer from scoliosis as well) but now the back brace doesn’t fit. How does one not have any recollection of being sickly or any side effects from the sickness? Even her sister was floored by these facts!! This was just the tip of the iceberg why I didn't like her!!

What upset me was the Mom was favoring the daughter that returned over Annabel that had been there the whole time.

To me there were so many red flags with Lydia that made me want to scream and if I was not in public I would have.

[Lynn · Rating 5 out of 5]

I received an advance reader copy in exchange for an honest review.

Genre: Psychological thriller
Rating: ⭐⭐⭐⭐⭐

When missing child Lydia returns home after six years, it should be a miracle reunion — except her sister Annabel takes one look at her and knows: that’s not my sister. But is Annabel right, or is grief and trauma shaping what she believes?

The story reveals key information at exactly the right moments, constantly shifting your assumptions. Every time I thought I had the twist figured out, the book pulled the rug out from under me again. The tension builds steadily, and the emotional connection to the characters, especially Annabel, made the mystery even more compelling. I loved her older-sister perspective and punk-inspired personality, which made her feel distinct and real from the start.

This is a great fit for readers who enjoy strong character development and psychological tension over nonstop action. The pacing is more slow-burn until the final stretch, which worked well for me but may not suit readers looking for immediate thrills.

A gripping, twisty read that kept me guessing until the end. Highly recommend for psychological thriller fans.

[The Chapter Belle · Rating 4 out of 5]

This was such a unique thriller, and I absolutely ate it up!

Six years ago, Annabel’s younger sister, Lydia, disappeared without a trace. Not long after, their father abandoned the family as well, leaving Annabel and her mother, Wendy, completely devastated. In the aftermath of Lydia’s disappearance, Wendy all but withdraws from Annabel, making an already traumatic situation even worse.

Then, six years later, there’s a knock at the door.

Lydia has returned.

Except…something isn’t right.

The family dog doesn’t recognize her (and is actually afraid of her). She claims she can’t remember anything about her childhood or her life before disappearing. And her behavior is strange enough that Annabel becomes convinced this girl isn’t really Lydia at all.

But Wendy is simply overjoyed to have her beloved daughter back and is determined to care for her - no matter what.

Full of twists, secrets, unease, and a creepy, claustrophobic atmosphere, this was such a gripping psychological thriller. I couldn’t wait to see how everything would unfold!

Highly recommend!

Huge thanks to NetGalley and Bookouture for the ARC!

[Angel **Book Junkie** · Rating 3 out of 5]

Thank you to NetGalley, Rosie Walker, and Bookouture for the copy in exchange for an honest review.

This book was dark — emotionally heavy and honestly heartbreaking at times. It really pulled at my heartstrings and explored some difficult themes that stuck with me long after I finished.

That said, the first part of the book was a struggle for me. I kept waiting for things to really move forward and felt like I wasn’t getting anywhere for a while. When “Lydia” suddenly appeared, it almost felt like I had stepped into a horror story — especially considering the title — and I wasn’t sure where the story was trying to take me.

But then… around the 75% mark, everything changed. The twists and revelations completely caught me off guard and finally delivered the emotional impact I had been waiting for the entire time.

Final verdict: A slow start that required patience, but a powerful final stretch that made the journey worthwhile. Dark, emotional, and ultimately memorable — even if it took a while to get there.

[Serena · Rating 5 out of 5]

Twelve-year-old Lydia vanishes without a trace, leaving her sister Annabel and their mother Wendy shattered. Soon after, Annabel’s father walks out, and the family fractures completely. Six years later, Lydia suddenly comes home, alive, older, and with significant gaps in her memory. Wendy is overjoyed. Annabel is not. Even the family dog doesn’t recognize her. As Annabel grows increasingly convinced that this girl is not her sister, the story spirals into a tense psychological game where nothing, and no one, feels entirely reliable.

This is a slow-burn psychological thriller that rewards patience. The suspense builds gradually, tightening chapter by chapter, until it becomes genuinely head-spinning. I loved how Rosie Walker keeps the reader constantly off-balance; I went back and forth repeatedly on who was unraveling faster: Annabel, Wendy, Lydia… or possibly all three. That uncertainty is the hook, and it’s executed beautifully. I lost sleep with this one and found myself irritated when real life (rude) interfered with my reading time.

Content-wise, readers should be aware of themes involving child disappearance, family trauma, abandonment, and psychological manipulation. None are handled gratuitously, but they are central to the story. My only minor critique is that the pacing may feel a touch slow for readers who prefer nonstop action, but for me, the creeping dread was exactly what made it so effective. I think fans of Gillian Flynn and Freida McFadden will feel right at home here. This was a compulsive, unsettling, and very satisfying read, and an easy five stars.

A special thank you to Bookouture for providing this book for review consideration via NetGalley. All opinions are my own.

[Diane Elizabeth Taylor · Rating 4 out of 5]

Rosie Walker is the queen of suspense! In this excellent novel, the warmth of a homecoming is quickly replaced by the chilling realisation that some secrets were safer when they were still missing.
In a quiet Edinburgh suburb, we meet Wendy, a devoted mother clinging to her social media and precious followers six years after her daughter Lydia’s disappearance.
When Lydia suddenly returns, the fragile peace between Wendy and her estranged daughter Annabel shatters. ​
The dual-perspective narrative is expertly paced, shifting from grief-stricken hope to a claustrophobic sense of dread.
Walker’s strength lies in her character depth, you’ll find yourself fiercely rooting for Annabel as the family’s polished veneer peels away.
It’s an emotional, twisty ride that culminates in a shocking final twist you’ll be thinking about long after the final page.
My thanks to Netgalley and Bookouture for an early copy. This is my own opinion voluntarily given.
Expected publication date 4 March.

[Joan Jordan · Rating 5 out of 5]

Lydia went missing at age 13 and suddenly reappears six years later with very little memory of her disappearance nor her life before. Though her mother, Wendy, immediately welcomes her back into the family, her older sister, Annabel, is not convinced that Lydia is who she says she is. Wendy defends Lydia against every accusation that Annabel makes, but Annabel is determined to prove that Lydia is an imposter and to find out what she wants. When she uncovers some strange things in Lydia's room, including notes about the family, Annabel decides that she will stop at nothing to expose this fraud and find out what happened to her sister all those years ago.

This is a book that I could not put down. Annabel is a bit of a prickly character, but Lydia and Wendy are not quite right either, and what happened to the dad? The questions surrounding each character make for great suspense and a surprising ending.

Thank you to NetGalley and the publisher for the ARC. All opinions are my own.

[Andria Lambert · Rating 5 out of 5]

There are three main characters, Wendy, Annabel, and Lydia. At the beginning of the story, Lydia reappears after having disappeared six years ago. Nothing is known about where she's been, what happened to her and she's not really telling much either. Wendy(the mother) takes her in with open arms, while Annabel wants it to be her sister but she just knows that this person isn't her sister. She sets out to prove that this person is an imposter, which pits her against her mother and "Lydia". Situations turn ugly and nobody or anything is at it seems. I was totally invested in Annabel and I kept rooting for her! There are some wild twists and turns that kept me guessing where the story was going, who the true villain was, and how it was all going to end up. I thoroughly and absolutely loved the story, it kept me hooked all the way through! Would certainly enjoy reading other books by the author!

[Vanessa Croft · Rating 3 out of 5]

I read Not My Sister via an eARC from NetGalley.

Told from the perspectives of both the mother (Wendy) and sister (Annabel), this book explores the aftermath of a family upon the return of its missing daughter (Lydia). The writer does a good job of developing the characters and positioning their POV, however much time is spent on internal monologue which took away from the general pace of the novel. Some of Wendy's moments felt very repetitive and I found myself wishing she would just get on with it since we already had spent so much time on her emotions regarding her daughter's return.

Overall, the twist was precisely what I had expected and I found myself reading not because I wanted to find out what happened, but because I was enjoying Annabel's character arc.

Readers who like the accessible narrative style of Freida McFadden will enjoy this novel.

[KKEC Reads · Rating 5 out of 5]

Not My Sister by Rosie Walker
HOLY CANNOLI. The way this story traveled and played out took me by surprise. I wasn’t quite sure which way things would go, and I was definitely shocked.

It takes such talent to write a character that readers are sure to dislike, and Wendy was that character. She was a terrible mother. Her arrogance was gross, and my heart hurt for Annabel and Lydia.

This was devious in so many brilliant ways. The subtle hints laid along the way that led to the big reveal were genius. I was hooked.

The alternating narrators both helped add to the instability of the storyline, which, in turn, made the plot thicken deliciously. This has everything a thriller requires and then some.

The writing was brilliant, the characters were well developed, and the plot twist was insane. This is a must-read!

Publication date: March 4, 2026
Publisher: Bookouture

[Tamara · Rating 4 out of 5]

A girl stands on the doorstep, her hands tremble and her eyes glisten with tears. My sister has finally come home after six long years.

I gasp in disbelief when I meet my younger sister’s gaze. I can’t believe I’m looking at Lydia’s sweet face again. We’d been so close as children. Then one day she didn’t come home from school, and she disappeared without a trace.

Not My Sister will have you second guessing yourself. The secrets will be exposed. Who is telling the truth? What/who is hiding in plan sight? You will have to read it to find out. It starts out a little slow. But will keep you engaged.

Thank you Netgalley and Bookouture for my ARC in exchange for my honest review. Highly recommend.

[Erica H · Rating 4 out of 5]

Review of advance copy received from Netgalley.

Of the books, I read this week, this was the one I most wanted to pick back up to see what happened next. Where a lot of thrillers start to sound very similar or have plot twists that ruin the whole book, the twists in this book just kept making it better. One aspect that I really liked about the book is that at first, you don't know which character you supposed to root for; it kept things interesting. I was invested and had to keep reading.

This was my first Rosie Walker book, but I just added the Bride's Secret to my TBR list. I rated this book 4.5 ★s out of 5.

[Britney Ireland · Rating 4 out of 5]

I voluntarily requested this book from NetGalley for an ARC copy in turn for my honest opinion.
Thank you NetGalley and Bookouture for the ARC read.

I enjoyed this book very much.

Imagine your sister who has been missing for 6 years shows back up on your doorstep after all that time. Your mom welcomes her home with open arms but you cant quite seem to believe that she is who she says she is.

This book has twist and turns that you wont see coming which makes it a great mystery thriller from start to finish.

Thank you again #NetGalley and Bookouture for the early read. I highly recommend.

[Maja · Rating 5 out of 5]

First things first, thank you Netgalley and also Bookouture for this ARC!

Secondly, OMG, I thought I already reviewed this and was totally shocked when realizing I did not! Also because this book does deserve better! After The Bride's Secret this was my second Rosie Walker book - I think? - and it was yet again brilliant! Devoured it within a day because I simply had to know what was going on!

Ask yourself - what would you do when your long-lost sister stands on your doorstep one day. You are happy to be reunited. But stomething does not add up. There are holes. There are things your sister claims not to remember. So, the question is - can you really trust her? Very much recommended!