Secret Sister

by Sarah A. Denzil

What if the person haunting you… had your face?

Faye Mathis has spent her life writing bestselling novels about identical twins who solve crimes together. But after she’s diagnosed with early-onset dementia, her world begins to blur around the edges.

Then a shocking photograph goes viral.

It shows Faye wandering half-naked through the streets in the early hours. Her daughter insists it’s her. Faye is certain it isn’t. But how do you prove your innocence when you can’t trust your own memory?

As disturbing coincidences mount—a woman claims to have seen her on the moors, her doors are found unlocked, and someone seems to be watching the house—Faye begins to wonder if she’s losing her mind or if someone is deliberately driving her mad.

When she uncovers a devastating secret about her past that shatters everything she thought she knew about herself, Faye must confront the terrifying possibility that the stranger haunting her might not be a stranger at all.

Perfect for fans of Freida McFadden, Shari Lapena, and Lisa Jewell, Secret Sister is a chilling psychological thriller about identity and ruthless obsession.

Genres: Audiobook, Thriller, Mystery, Fiction, Crime, Mystery Thriller, Psychological Thriller

314 pages, Kindle Edition

Published April 7, 2026

About the author

Sarah A. Denzil is a Wall Street Journal bestselling suspense writer. She is also known as young adult author Sarah Dalton.

Sarah lives in Yorkshire with her partner, enjoying the scenic countryside and rather unpredictable weather.

She is the author of international bestselling psychological thriller SILENT CHILD, which topped the bestseller lists on Amazon in the US, UK and Australia.

You can read now read AIDEN'S STORY, a short story and sequel to SILENT CHILD. It's completely free here: https://dl.bookfunnel.com/n7lb74chp3

Find out more at: http://www.sarahdenzil.com/

Join the newsletter for updates: http://eepurl.com/cwAmZD

Follow her on Facebook: https://www.facebook.com/sarahadenzil

Check out her Instagram page:
https://www.instagram.com/sarahadenzil/

Email: sarah@sarahdenzil.com

Reviews

[☮Karen]

2 stars.
This was a freebie on Audible so I'm glad not to have spent a credit or any cash on it. Very strange transitions between chapters / points of view, music, and sound effects on the audio had me losing patience with it repeatedly. Not very likeable characters or realistic plot. I finished it though! I don't know why!

[Tuesdaybeanreads]

Honestly, this one just didn’t do it for me. The premise had potential, family secrets, drama, a mysterious sister? I was intrigued. But the execution fell flat. The pacing was all over the place, and I struggled to connect with the characters. Some of the plot twists felt forced or way too convenient, and the emotional beats didn’t quite land for me. Not the worst thing I’ve ever read, but definitely not something I’d pick up again.

[Fred]

3.5/5 – A good thriller overall, but with several loose ends. The police characters are especially frustrating — arguably the most useless in the entire book. Also, the sound effects feel random and out of place; if you're going to use them, at least be consistent throughout the chapters.

[Kara Ayres]

If I could, I’d rated this 2 1/2 out of five stars. Cheap sound effects annoying music and parts of the book made you simply want to scream and not in a good way. If it’s not clear, I read the audiobook version of this. narrators were professional and proficient, but in my opinion not one of Sarah Denzel‘s best works.

[Jo Lee]

2.5 🌟
3 stars for the story which was good if a little bit loose.
2 🌟 for the full cast of narrators
1🌟 for the childlike sound effects. These were really unnecessary and too sporadic to actually add anything.

[Tracey Kiser]

Annoying music between chapters and sound effects while listening to Creepy storyline.

[Mike Finn]

'Secret Sister' (2025) is an Audible Original, written by Sarah A. Denzil ('Silent Child', 'The Housemaid', 'The Woman In Coach D') and narrated by Jessica Gunning, Sacha Dhawan, Joanne Froggatt, Nathaniel Curtis, Hopi Grace.

This is a project Audible have put money into. The production standards are high. It's a powerful audiobook.

It opens with a man digging a grave in the dark of the night on a Yorkshire moor for a woman who is not yet dead. Things do not go to plan. Then it shifts to our heroine, Faye Mathis, who is living alone in her house on the moors. Faye is a fifty-year-old, divorced, best-selling author of children's books about a pair of sleuthing teenage twins. She's recently been diagnosed with dementia and believes she will soon no longer be able to function.

It's a great set-up that gets even more intense when it becomes clear that there are some secrets associated with Faye's adoption that may now pose a threat to her.

The story is well-told and well-narrated. It gets more and more intense. There's a rich suspect pool of people who may be ready to betray Faye, possibly even kill her. Faye is struggling to understand how much of what's going on is real and how much is a side effect of her dementia-produced paranoia.

At the start of the book, I was pulled along by my curiosity about Faye and her situation. By the time I was halfway through the book, I'd grown to like Faye and to understand how vulnerable she was and how much malice was heading her way. I realised two things. Firstly, the rest of the book was likely to be about very unpleasant things happening to a vulnerable woman. She might survive it all, but she'd go through hell first. Secondly, I had no desire to wade through that, no matter how well done it was. It was too real and too upsetting. 

I like my thrillers to be thrilling. The thrill should be believable enough to keep me engaged, but not so real that thrill turns to upset. This started to feel like I was inflicting trauma on myself in the name of entertainment.

[Romulo Perez-Segnini]

A convoluted story with too many similarities to make it reasonable. A famous author that has been diagnosed with early stage of dementia is photographed disheveled one morning. She has no recollection and starts to believe she has a twin sister. She knows she’s adopted but never wanted to learn about her biological family.

Eventually we find out that she does have a twin sister and both of them have evil stepsons. The story abuses the notion of dementia. Sometimes she’s fairly lucid and others she’s completely lost in her thoughts. Anyway, there are other illogical factors that complicate the plot.

The ending is as absurd as most of the narrative but not awful, so three stars seems fair.

[Julinda Hopkins]

I thoroughly enjoyed this audiobook. The suspenseful vibe was easily achieved. I was coaxed along into different speculations of what was actually happening. The narrators brought the characters to life, or death, in engaging portrayals. It was an extremely well done production. So, I'm not sure who gets the most credit, the author or the narrators. I say, both. Well done!

[Stephanie Wright]

I listened to the audiobook and the music between chapters was so annoying. I know that sounds picky, and I don’t MIND music, but it just didn’t match the vibe of the book AT ALL. Like, the chapter would end on something super serious and scary and then UPBEAT ACOUSTIC GUITAR 🎶. 😑

[McKenzie Martines]

It was too long.

also, hate the background noises and effects for the audible originals.

[Diane 🌻 Williams]

Story 5/5

Narration 5/5

Musical Interludes 1/5

Loved, loved, loved the story and characters. The story had me on edge quite a few times. All of the characters were fully developed, even those introduced later in the story.

My ONLY complaint is the music. I still don’t understand why it was used before certain chapters and not others. Either use it before all (I’d rather you didn’t) or none. Plus it was not always the same piece of music. I’m so confused 😐 😂

Am I glad I read it? Wholeheartedly!

Would I recommend it? I would highly recommended reading the book vs listening to the audiobook because the music really ruined the experience for me.

[Aggie]

This was an interesting read. I’ll look forward to book 2.

[Leah Orr]

Listened to this on Audible. Great twist. Thoroughly enjoyed it. Nice quick listen.

[Angela]

I did not really like this book. It felt like it dragged and I just wanted to get it finished. Also, while I felt the author did a decent job with some of the twists others felt predictable. Also I felt like it wasn’t believable in some parts. For example, you are a famous author who has a twin sister you never knew about but you’re famous enough to be in the tabloids? Surely someone would have mistaken your twin for you previously.

[Sophie]

I really enjoyed this thriller! We find out enough about each character as the book goes on that it kept me interested, rather than waiting until the end in one big reveal. Obviously it’s very unrealistic but enjoyable all the same

[Linda]

Audiobook. Decent thriller, great start, goes slack about 2.5 hours from the end, but rather nice roundoff. The highlight was the narrations: all great and Jessica Gunning the cherry on top.
I travel a lot for work, so this was an entertaining road companion.

[April Wick]

Loved this book from start to finish!! Some made comments about the sound effects but they were brilliant.

[Laura]

I saw that Joanne Froggatt narrated this, and that is why I chose it. I loved her in Downton Abbey. This was twisty with lots of surprises, and I enjoyed it. I don’t want to give anything away.

[PugMom]

I really enjoyed the story but was not a fan of the sound affects and male narrator.

[Jennifer Rodriguez]

Wow!! This one definitely had the twists, If you thought your family has issued smh nope this one is up there. Nice little Audible thriller.

[navelliaa_books]

C’est mon 2eme livre audio de Sarah A. Denzil et tout ce que je peux dire c’est qu’elle est trop forte. La qualité de l’audio est géniale. Et cette histoire purée j’ai adoré ✨

On est sur un thriller angoissant, une femme de 50 ans, autrice à succès avec de l’alzheimer précoce. Un jour, une photo d’elle sur les réseaux sociaux sort, et on l’a voit dans un piteux état. Sauf qu’elle ne s’en rappelle pas. Qu’est-ce qu’elle a fait ?

C’est hyper addictif parce que chaque chapitre nous fait douter, chaque chapitre nous fait réfléchir et chaque POV est intrigant. Donc, ça se lit (s’écoute) vite car on a besoin de savoir.

La protagoniste principale est ultra attachante je trouve. Elle m’a fait beaucoup de peine, notamment dans sa relation avec l’Alzheimer par rapport à sa fille.

Bref, c’est un thriller addictif, bien écrit et intéressant.

[BossyLadi]

dnf
I have no idea what I was just reading. I gave up.

premise: one storyline is about a writer getting dementia. another storyline is about that writer researching her adoption.

we also have a mysterious, evil sister? no clue why.

we also have someone called a grave digger. no clue why.

i think the mystery/suspense involves the sister and the grave digger but I'm well into the book and have no idea what/ why/ how.

[Angela]

Audio book was ok. The added theatre sounds like doors shutting, typing sounds, etc to illustrate what was happening in the book were ANNOYING!! I’m trying to read (listen) to a book, not watch a movie. Story was confusing, but enjoyable.

[Clare Crawshaw]

A great read, A bit confusing with so much character changes but still good, very disappointing last chapter though which is why it hit 4 and not 5 stars

[Lucy Platt]

great story, loved the twists

[Diane Merritt]

Fabulous twisty book that leaves you wondering even until the very end. Sarah A. Denzil outside herself with this book.

[Madelyn Messick]

I binged this in less than 24 hours! It was so good! The twists were ones I never saw coming.

Sounds like other people reading it didn’t like the audio book version- this might be a better one to physically read.

[Roksolana]

The story started on a promising note about a mysterious adoption story. But it continued messing up the storylines and the plot, making it extremely predictable. Also, the fact that characters are not put off by murdering other people is surprising.

[Paul McDonald]

A triangle of intrigues, linked by blood. A story with a few twists, enough mystery to keep you reading. At times I wondered about the characters actions but overall a good read.