Grave Waters

Cassidy Knox #3

by Shannon Hollinger

Most federal agents can go their entire career without encountering a serial killer. For Cassidy Knox, it’s starting to feel like she’s collecting them.

With her retirement from the Bureau looming on the horizon, FBI Special Agent Cassidy Knox is focusing on her new life, one that’s filled with running the animal sanctuary she inherited... and a budding relationship that’s heating up. But when the body of a man is pulled from beneath the murky waters of the Florida Everglades, locked in a giant crab trap, a personal connection to the victim drags her back into the darkness she longs to escape.

Jumping deep into the investigation, what began as a reluctant favor takes a terrifying turn as Cassidy uncovers that the tiny town of Gator Glade has a serial killer on its hands. Still bearing the scars of her last encounter with that kind of evil—one that she barely survived—she’s forced to confront her deepest fears.

As a stalker watches her every move and darkness creeps closer, Cassidy races to untangle the twisted links between the victims. But as she digs deeper, she uncovers a chilling connection—and realizes the hunter is lurking closer to home than she ever imagined. With danger around every corner and eyes following her from the shadows, will she once again find herself in a killer’s grasp?

Dive into Grave Waters for a thrilling blend of mystery, suspense, and romance that will have you turning pages late into the night.

251 pages, Kindle Edition

Published March 27, 2026

About the author

With degrees in Crime Scene Technology and Physical Anthropology, Florida writer Shannon Hollinger hasn’t just seen the dark side of humanity—she’s been elbow deep inside of it! She’s an avid animal lover, reader, and hiker, and has been known to use her forensic skills to figure out who ate the last cookie in the house.

A multi-genre, Amazon charts top 20 best-selling author, Shannon writes psychological thrillers filled with jaw-dropping twists and shocking endings, the police procedural Chief Maggie Riley mysteries, where the darkness of the Maine wilderness is rivaled only by the deadly secrets it conceals, and the romantic suspense Cassidy Knox mystery thrillers, where the animals will steal your heart and the nights are as hot as the days.

Her novels have been translated into multiple languages, and her short fiction has appeared in Suspense Magazine, Mystery Weekly, and The Saturday Evening Post, among many other magazines and anthologies.

Shannon is a member of the International Thriller Writers and the Short Mystery Fiction Society.

To keep current on book news and to enter monthly giveaways, sign up for Shannon’s newsletter through her website, www.shannonhollinger.com.

Find Shannon on social media:

https://www.facebook.com/thiswritersays
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https://www.tiktok.com/@shannonhollinger
http://www.pinterest.com/thiswritersays
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Reviews

[Katie Mettner]

Just when you think Cassidy and Jake surely can't get into any more trouble, they prove you wrong. In Grave Waters, they prove you wrong in a BIG way. With a serial killer on the loose in Gator Glade, Cassidy is the only boots on the ground to help her director find the person before they strike again. Okay, that's not entirely true. She does have an agent from the Miami office who wants to help, but does he want to help? It seems to Cassidy that he has a bone to pick and when her life is on the line, that's the last thing she wants. This is a twisty, turney mystery of who the serial killer is, why they are after the man she loves, and how she is going to find him before he takes the only person she has left in her life. There were plenty of tense moments in this book, but also lots of hilarity from our protagonist, who has a great sense of humor despite what she's dealing with. The tender moments really got me, though. We got to meet the real Cassidy Knox in this book. The Cassidy without the badge, and I really like her. I can't wait for book 4!

[Paulette]

If you like books with a complex plot, engaging characters and just enough red herrings to keep you guessing, then Gravers Waters is a must read. FBI Agent, Cassidy, is dealing with two mysteries and her relationship which had been heating up with Jake had cooled considerably and she didn’t know why.
An engaging mystery and I look forward to reading more of Agent Cassidy Knox.

[Samara Hepplewhite]

⭐️⭐️⭐️⭐️⭐️ ARC Review

A fantastic continuation of the series. The storyline in this third instalment was strong and flowed perfectly from where book two left off, making it incredibly easy to fall straight back into the world.

I absolutely love the characters, they’re consistently engaging and full of personality. Stephano remains my favourite!

A gripping read from start to finish, and now I’m even more excited to see what’s next for Cassidy Knox. Five stars!

[Carol Nauss]

"I don't go looking for trouble but I have a habit of finding it". So true of FBI agent Cassidy Knox. Life is not simple for Cassidy once bodies in crab traps start surfacing. There is a serial killer at large and Cassidy is quickly involved in finding the killer. I love this series and especially the tough, resilient character of Cassidy. The plot is suspenseful and has twists I didn't see coming. Each book in the series builds on the prior book but can be read as a standalone, but do yourself a favor, and read the entire series. You won't be disappointed.

[Sheri]

Cassidy works for the FBI, although that is uncertain at the beginning of the book. This series can be read as standalones but since the character arcs travel seamlessly from one book to the next you will want to res the whole series at some point. It does not need to read in order to fully enjoy the series.

I fell in love with Cassidy from this book. She is a friend you want on your side. I can’t wait to see where her next adventure takes her!

[Dawn]

I really love this series! Cassidy and Jake are excellent characters that you just want to keep reading about book after book. Cassidy is called in and reinstated to find a possible serial killer. All roads lead to someone at Jakes job. Does Jake know? Who and why are men being killed? You have to read to find out. I literally read this book on one day. It's SO good !

[Denise Little]

I absolutely was engrossed in this one! So happy to see what Cassidy and Jake are up to. Cassidy runs an animal sanctuary and is pulled back into the FBI when a man is found dead in a crab trap. It seems there is a serial killer in her town.

This one is filled with mystery, suspense and even some romance. A must read!

Release date March 27, 2026

[Rachel Browning]

“Grave Waters” by Shannon Hollinger is another fantastic Cassidy Knox thriller that completely pulled me in. Cassidy once again puts herself in serious danger while tracking down a serial killer, and the tension never lets up. The risks she takes and the trouble she finds herself in had me hooked from beginning to end. I read this in one sitting and couldn’t put it down. This series just keeps getting better, and Cassidy Knox is such a compelling, fearless character. I can’t wait for more!

[Bella Crooke]

book 3 of the Cassidy Knox series was PHENOMENAL!!!!!! I just love this series and shannon’s writing style is easy to follow I LOVE the little goat Stephano!! The ending had my JAW ON THE FLOOR!!!! I am SO EXCITED for book 4!!!

[Justice Singh]

ARC review :

If you love twisty fbi thriller type books this is a good one. Recently came across this author and I’ll be following for more from her.

This is a series but can also be read as standalone which I love as well.

It’s fast paced which makes it interesting so you don’t lose focus or interest in the story and the storyline itself is enough to keep you wanting more! Definitely recommend

[Bola]

I really enjoyed playing detective alongside Cassidy Knox in this one. Even though this is book 3 in the series, I didn’t read the first two and still found it easy to follow as a standalone.

If you like detective-based thrillers, this is a solid pick. I also appreciated the touch of romance woven into the story—I was definitely rooting for Jake and Cassidy.

Overall, an engaging read with a good balance of mystery and character dynamics!

[Heather Flaherty]

I am loving the Cassidy Knox series and this third book is phenomenal! Cassidy’s life is going great for once and things with Jake are incredible. As a favor to a friend, she jumps in to try and figure out why a man was just pulled out of the water. Enter a serial killer. Victims start surfacing in crab traps and someone is stalking her. Can she expose this killer before she is the next victim?

[Maureen ~Bitch Can Write A Book]

Welp. She did it again. This may be my favorite one so far. Every book just gets better. Great characters and I literally want to climb in the book and visit this animal sanctuary. I’m looking forward to getting back to this crazy town…Gator Glade. Cassidy Knox is quickly becoming a favorite charter!

[Debra]

Shannon Hollinger and FBI Special Agent Cassidy Knox are back in another thrilling, gripping, tense, and hard to put down book!!!!! Grave Waters is the third book in the stunning and wonderfully written Cassidy Know series! I appreciate that this book takes place shortly following the events of the second book in the series, Fatal Betrayal. While this book would work as a stand-alone, I highly recommend reading the first two books in the series to become better acquainted with Cassidy and Jake. The first two books were intriguing and thrilling and had me on the edge of my seat. Grave Waters is the 11th book that I have read by Shannon Hollinger.

Cassidy Knox just can't seem to catch a break! Can't a girl have a little down time? She is busy running the animal sanctuary she inherited, while helping Jake recover from his injuries. The chemistry between Cassidy and Jake is about to boil over until a man's body has been found inside a crab trap in the everglades. She is called back into action when the man's identity is known, and Cassidy can't say no as she has a personal connection to the man. When Cassidy learns of other men killed in the same manner as the dead man in the crab track, she knows she is searching for a serial killer!

As Cassidy begins her investigation, she welcomes a rooster to her animal sanctuary and finds herself in harm's way in more ways than one. Not from the rooster mind you, but from another source close to the rooster! Plus, the search for the serial killer ramps up and his Cassidy looking very close to home for answers.

This was another gripping and thrilling book in the series. I enjoyed the mystery and the unfolding of the plot. The tension and sense of danger grew as the book progressed. I also enjoyed the sense of community in this book. Cassidy returned to where she grew up after her grandfather's death. She knows many of the locals from school, and I enjoyed the few scenes with her exchanging banter with them. I also enjoyed the character development and continuation of the story arc. Plus, I love how the animals steal every scene that they are in!

Wonderfully written, well thought out, gripping, full of tension, unease and danger!

Thank you to Shannon Hollinger who provided me with a copy of this book in exchange for an honest review. All the thoughts and opinions are my own.

Read more of my reviews at www.openbookposts.com 📖

[Cheyenne Joy Mijdam]

ARC Review
⭐️⭐️⭐️⭐️
Release date: March 27, 2026
Grave Waters by Shannon Hollinger

First off: thank you Shannon for letting me read this ARC, and thanks to Inside Story for once again dragging me into a serial killer hunt I was absolutely not emotionally prepared for.

Let me start with the pacing, because honestly? My chaotic brain loved it. This book moves. No endless wandering around in circles, no twenty pages of staring at a wall thinking about life. It goes. And when a story moves like that, my brain stops wandering off to do taxes or question my life choices. So yes — points for that.

Also fun fact: I didn’t even realize this was part of a series. And somehow… it still worked. I never felt completely lost, which is rare. If anything it just made me curious enough to go back and shove the earlier books onto my already dangerously unstable TBR pile.

Now the vibe. The paranoia. The constant look over your shoulder feeling. I love that in a thriller. If a book doesn’t make me slightly uncomfortable, slightly suspicious of everyone, and mildly convinced the killer might be hiding behind my couch… then what are we even doing here?

Cassidy is the kind of character I like: capable, messy, human. She’s juggling an animal sanctuary, a relationship, loyalty to the people around her, and somehow also getting dragged into hunting a serial killer. Casual Tuesday activities.

And then there’s the ex-husband situation. Found dead. Underwater. Eaten by crabs.

Which immediately sent my brain down the worst possible thought spiral:
If crabs eat humans… and I eat crabs… am I technically participating in some weird seafood-flavored cannibalism situation?

Anyway. Sorry about that. If I ruined crab for you… well… welcome to my brain. I live here and it’s exhausting.

The story throws in enough twists and side paths to keep things interesting. Not the kind that completely shatter your soul, but the kind that keep you engaged and turning pages. I had theories. Many theories. My dark, twisted detective brain confidently accused about twelve different people.

I was wrong about all of them.

Which basically means if I ever end up working for the FBI, we’re all doomed.

Still, I had a great time reading this. It felt chaotic in a way I could appreciate, and I genuinely enjoyed being pulled into the hunt. So four serial-killer stars from me — mostly because some books emotionally scar me for life, and this one only messed with my brain a reasonable amount.

If you like fast-paced investigations, strong women trying to keep their sanity while everything around them burns, and a good old-fashioned serial killer hunt… you’ll probably enjoy this one.

Just maybe… don’t eat crab while reading it. Trust me on that. 🦀

[Tammy Lunsford - Escape to Books By Tammy]

FBI Special Agent Cassidy Knox is quickly becoming another favorite fictional character for me. She has nerves of steel and a backbone to match. She is trying to retire from the FBI, but retirement is once again alluding her, especially now that she has been asked for help by a former colleague. She has been temporarily reinstated to the FBI and drawn back into the dark mind of serial killer. I could not help but think about the fact that the wild animals that she cares for at her animal sanctuary were less dangerous than the serial killer she is searching for. At least with an animal, you know what you are getting into. This individual was walking amongst people looking perfectly normal. This one is personal and the dumping ground is in her backyard, which makes it even more personal.

My stomach was in knots the entire time I was reading this book. It was one of those mysteries/thrillers that make goosebumps come up on your neck. This individual was especially depraved. I mean who puts a human being in a giant crab trap and dumps them in the sea? The thrills were constant, as she is also dealing with an unknown stalker.

I am exhausted after reading this book. I also needed a round of cartoons as this one left me thrilled and chilled, but excited as well as I thrive on reading things that scare me.

I hope this is not the last book for Cassidy Knox. She is on my list of favorite characters to read about.

Thank you to the author for this ARC. I am leaving this review voluntarily.

[Joanne Dunn]

When is book 4 coming! The latest in the Cassidy Knox series, Grave Waters, by Shannon Hollinger is released later this month and is another great addition to the series!

While each book pulls you into a new crime that Cassidy is working, there are snippets from each book, making this an interconnected series. You can read each book as a standalone but recommend reading in order, for a greater understanding of all the characters and more in-depth background to elements of the story.

Book 3 is almost an instant continuation in the timeline, they are barely recovering from the impact the previous case has on them all, when Cassidy is asked by her boss to assist the local FBI field office, after her ex-husband is found murdered in a gruesome manner, and he is not the first. The hunt for this serial killer who is in her back yard will have her suspicious of those around her as strange things happen and danger comes to her door.

The opening of the book is instantly engaging and had me laughing when I realized what was going on, oops, hopefully I’m not giving too much away. The writing is engaging and the characters relatable, I couldn’t help nodding at how accurate the description of the struggles of a fair skinned person in the sun without being totally covered. I enjoyed learning more about each character, the interactions when Cassidy reconnected with those from her school days, and the happenings at the sanctuary.

[Sharon]

4.5 Stars.

Mystery crime thriller with a unique serial killer storyline. The killer locks his victims in a giant crab trap & dumps them into the sea to be eaten alive. Imagine eating crab that may have eaten human remains? Just ewe.

Our main character, Cassidy, is an FBI agent working to solve these unconventional murders, as well as dealing with a stalker of her own & on a lighter side taking care of her animal sanctuary at the same time. Her descriptions of the animals are a hoot & I especially loved Stephano, the pygmy goat.

This is the 3rd installment in the Cassidy Knox series which is fast-paced & kept me on the edge of my seat. Each book in the series can be read as a standalone, however I always read my series in order (except this one), so I feel like I missed some important aspects of Cassidy’s background. I will definitely be going back to read the first 2 in the series (DEADLY SANCTUARY & FATAL BETRAYAL) to get better aquatinted with her character. I am also looking forward to the 4th installment (BITTER TRUTH) coming soon.

I highly recommend this series. Be sure to read them in order. I believe it will enhance your reading experience.

Favorite Lines:
“If you ask me, there should be a personality test to match shrinks with their patients.”
“He’s the only shark in my pit with a soul.”

Thank you to Shannon & her ARC Team for an eARC in exchange for my honest review.

[Simone]

I absolutely loved this book! It was incredible!

I am completely hooked on the Cassidy Series, and while I was sad when this one ended, I was thrilled to learn that there will be a book #4.

As I expected, Grave Waters is even better than the first two books, if that’s even possible. I’m honestly still a little speechless.

I fell in love with Cassidy and Jake back in book one, and with every book my love for these characters has only grown stronger. Watching them develop throughout the series has been such a great experience as a reader.

The plot is flawless. Shannon Hollinger has an incredible writing style that completely pulls you in, you almost forget you’re reading because you feel every moment alongside the characters. The suspense and twists are wonderfully done and kept me engaged the entire time.

I highly recommend this series. While each book provides enough background to be read as a standalone, I definitely suggest reading them in order. Seeing the characters grow and evolve from book to book makes the journey even more rewarding.

Thank you so much to Shannon Hollinger and KM Lit Services for including me on the ARC team and providing me with an eARC in exchange for my honest review.

[Mercedes Narain]

This series just keeps getting better and better 🔥

Book 3 had me hooked from page one, and seeing Cassidy’s journey continue was everything.

Cassidy runs an animal sanctuary, trying to maintain some normalcy... until she’s pulled back into the FBI after a man is found dead. And just like that, everything spirals again.

Is there a killer in her town? Can she trust the FBI this time... or is she on her own?

I love Cassidy. She’s fearless, determined, and never backs down. She had me turning pages late into the night, saying, “Just one more chapter.”

The pacing is perfect, the chapters are short, and the twists are WILD.

Also, can we talk about Cassidy & Jake? Their journey across all three books adds the perfect touch of romantic suspense. And the animals at Cassidy’s sanctuary? Funny, unforgettable, and such a unique plus for this series.

If you love:
🔪 fast-paced thrillers
💪 strong female leads
🖤 serial killer investigations
🔥 twisty plots you won’t see coming

…this series is 100% for you. I’m already counting down to book four.

4.5 stars. Thank you so much to the author @thiswritersays for the complimentary copy of this!

[LitWithBritt27]

I’m so grateful to be part of Shannon Hollinger’s ARC team, this is my third early read from her and she just doesn’t miss. Grave Waters pulled me right back into Cassidy Knox’s world, and I love the chaos she somehow always finds herself in while juggling the sanctuary life.

Also, can we talk about these covers for a second? Absolutely gorgeous. Yes, I’m judging books by their cover and I’m not sorry 😝

This book had me hooked. The plot was engaging, the pacing felt just right, and those shorter chapters made it so easy to say “just one more.” The characters continue to feel real, even the ones you don’t like, which just proves how well they’re written.

I do have one request though, I need more backstory on Cassidy’s prior partner. I’m officially putting it out there for a prequel because I’d read that immediately. 😉 (hint hint!)

If you love fast paced thrillers, strong female leads, and a touch of romantic suspense, this series is absolutely worth picking up. I’m already counting down to book four.

Thank you to Shannon Hollinger for an early copy of this book, but as always, all thoughts are my own.

[Dani]

I was really looking forward to this one and to seeing what new *troubles* Cassidy would attract this time. I like her character a lot. She doesn’t let her past define her, and her decision to stay in the small town she grew up in—and take over the animal sanctuary—felt like a natural next step for her. And honestly, I’m falling a little bit in love with all the animals too. 🙂

She was ready to say goodbye to her former job, but it seemed like the job wasn’t quite ready to let go of her. When her boss asks her to help solve a series of murders, she’s pulled into yet another situation where she forms unexpected friendships, fears for her life, and has to prove her worth—mostly to the men she finds herself working with.

The author clearly knows what she’s doing, and it shows. The investigative elements feel well thought out, and the way Cassidy approaches uncovering the truth comes across as grounded and believable.

I've become a fan of the writing style of the author and hope, that the next book in the series will come rather sooner than later.

I received a free copy of this book and am voluntarily leaving a review.

[Janilyn Kocher]

Let me rave about Cassidy Knox #3
Cassidy gets into more trouble than most people contend with their entire lives.
For some of the scenes I was back in the 1980s watching episodes of Remington Steel because it was torture to see the 2 people you want to hook up, keep getting close but then they’re interrupted! Argh!
Rowdy Rooster joins the sanctuary and he loves to wrestle with hoses, which was hilarious. There were many amusing scenes that I got a good laugh out of.
There’s also a very sweet scene toward the end among the tools at a store.
Jake needs to feel needed by Cassidy and finally he gets his opportunity!
What is it with the Miami Office Morons??
I was wrong about one character who projected sliminess only to discover the sliminess was actually two other creeps.
There are many suspects in the swamp and I still want Chomp to have a live feeding opportunity!
Thanks to author for the advance copy!

[Chapters_with_VDKeck]

Y,ALL! Just as Cassidy is preparing for retirement—dreaming about her animal sanctuary and a budding romance—a body turns up in the murky Florida Everglades… stuffed inside a giant crab trap. Yep. Things escalate fast. What starts as a reluctant favor quickly spirals into a chilling hunt for a serial killer hiding in the small town of Gator Glade.

Shannon Hollinger delivers sharp writing, fantastic character development, and breakneck pacing that makes this book ridiculously hard to put down. Cassidy is tough, layered, and impossible not to root for as danger creeps closer with every clue.

Dark, twisty, and seriously addictive—this thriller will hook you fast and refuse to let go. If you love high-stakes suspense, grab this one! 🐊📚

[Alexandra]

This was my first read by Shannon, thank you so much for the ARC!

I’ve heard this can be read as a standalone, and while you can, I do think I would’ve enjoyed it even more having read the first two books to really know the characters more going in.

Cassidy is stepping into a new chapter of her life, but somehow trouble always seems to find her… and in this case, it’s a serial killer.

At the same time, she’s trying to navigate her relationship with Jake and take things to the next level, but that’s not exactly easy when there’s an active case that hits a little too close to home, especially with its ties to Jake’s firm.

It was an engaging read that kept me turning the pages, though it didn’t fully click with me overall.

[Beth Moylan]

I really enjoyed this series. Grave Waters is the 3rd in the series. I love the characters. Cassidy and Jake are so easy to love and to route for. Cassiday Knox was retiring from the FBI and only going to be a consultant on a part time basis. However, when Cassiday's boss's ex-husband is found murdered, and is part of a serial killer, she asks Cassidy to be reinstated and to help find the serial killer. Cassidy wanted to help her boss but at what cost. while looking into the victims and what they have in common she determines that they all had something to do with Jake's firm. Everyone she meets from the firm is a suspect. Will she find them in time to save Jake and herself. This was such a gripping, edge of your seat and wonderful page turner. You will enjoy this as much as I did.

[Kayla Wiklanski]

Would you like some crab 🦀?

Maybe not after reading this story 😉. To rid of the victims the serial killer feeds them to the crabs 😳.

Cassidy's determination to find who the killer is, puts her in a tight spot. Even with her trauma, that's she's progressing through, she still has an uncanny ability to solve cases.

I couldn't stop reading this book. It latches on and screams keep reading me. I was shocked how quickly I flew through it. I love how the story flows effortlessly from Deadly Sanctuary to now Grave Waters. There's no time gaps, each book picks right up where the other ended. This series just gets better and better.

[Rick Molitor]

This series just continues to get better and better. Cassidy once again draws trouble to herself like a magnet. Cassidy is pushed into investigating a serial killer who has claimed her boss's ex-husband as one of his victims. The clues point to it being someone who works at her boyfriend Jake's firm. This is a wild ride that will keep you on the edge of your seat as Cassidy works her magic. I book not to be missed.

[Harmony E. Jacobs]

Review of advanced copy‼️

Shannon Hollinger didn’t disappoint with this incredible Cassidy Knox thriller. And I really love how you become instantly hooked with the story from the very first page. I honestly also love a great psychological thriller similar to Silence of The Lambs and Grave Waters definitely gave off that vibe. I also loved the pacing of the book as well. It allowed the plot to flow seamlessly. Great Job‼️ Look forward to reading the next book in this series.

[Tillb1ta]

Pleasantly surprised that I didn’t see the connection in the conclusion of this story. It had my attention from page one. Great format to read and the characters were brilliantly brought to life. Truly enjoyed this thriller and look forward to the next one.