Deadly Sanctuary

Cassidy Knox #1

by Shannon Hollinger

She’s no stranger to trouble…

Deep in the heart of the untamed Florida Everglades lies a web of secrets, danger, and deceit. For FBI Agent Cassidy Knox, it’s the only home she’s ever known—one she vowed never to set foot in again. But after a harrowing confrontation with a serial killer, Cassidy finds herself with no choice but to return to the animal sanctuary of her youth. Grieving the recent death of her beloved grandfather, Butch, on top of her own trauma, she hopes for a brief respite to heal her wounds.

Only the swamp, where the past lurks just beneath the surface, has other plans. When a neighbor is found murdered, the suspicion surrounding her grandfather’s death intensifies, drawing Cassidy into a chilling investigation that threatens everything she holds dear. With old friendships rekindling and new betrayals surfacing, the lines between ally and enemy blur.

As Cassidy races against time to uncover the truth, she clashes against her inner demons—and the boy who once stole her heart. With danger lurking around every corner, the only thing she knows for sure is that she can’t trust anyone. Because the killer’s taking aim… and they have her in their sights.

Get ready to dive into a heart-pounding mystery where trust is a luxury and survival is a game of wits. A gripping, heart-racing thriller that will leave you breathless.

Genres: Thriller, Suspense, Fiction

256 pages, Kindle Edition

Published September 8, 2025

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
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Reviews

[Debra · Rating 4 out of 5]

Who says you can never go home again?

Secrets, lies and deception are the name of the game in Deadly Sanctuary! I was instantly engrossed in this book from the very first page! FBI Agent Cassidy Knox has survived a horrific trauma and is attending the funeral of her partner when she receives a phone call that devastates her. Her grandfather, Butch who raised her, has sadly passed away. Cassidy needs to return to the Animal Sanctuary in the Florida Everglades that she once called home to get his affairs in order.

While trying to get his affairs in order, Cassidy encounters old friends and classmates she knew growing up. It has been twenty years since she left, and news of her return has gotten around. Plus, she has the animals at the sanctuary to help care for and I have to say several of them stole very scene they were in!

Cassidy is dealing with PTSD from the trauma she survived while grieving for her grandfather. She is one tough cookie but also vulnerable and she soon wonders who she can trust when it appears her grandfather's death may not be from natural causes as was initially believed. When another person in town is murdered, Cassidy vows to get to the bottom of things.

Like Cassidy, I wondered who could be trusted? There were several characters who made my suspect list and Shannon Hollinger does a great job at keeping readers guessing. I enjoyed the mounting tension and the sense of dread that seeped from the pages. I also enjoyed the suspense and the not knowing who could be trusted in the small town.

Gripping, tense, shocking and mysterious! This is the 9th book which I have read by Shannon Hollinger, and she has captivated me with her well thought out riveting plot once again! I enjoyed Cassidy's character and look forward to getting to know her more in future books.

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 📖

[Tina Loves To Read · Rating 5 out of 5]

This is a Mystery/Suspense, and this is the first book in the Cassidy Knox series. I really loved this book, and I will be reading the next book in this series. The suspense and mystery kept you wanting to read and kept you pulled into the story. I loved this book so much.

[Janilyn Kocher · Rating 4 out of 5]

I always love a fresh new series that involves a woman jn law enforcement!
Cassie is trying to recuperate from a harrowing incident that got her partner killed and now her beloved grandfather is gone.
So back to the sultry steamy swamp she goes to figure out what’s next.
I liked seeing Cassie get her resolve and backbone back! I especially liked how she dealt with the blowhard sheriff at the end.
I didn’t trust one person instantly because they came in strong and insistent—-red flag.
I warmed up to Jake immediately but didn’t know if he was trustworthy.
The animals stole some of the story from Cass. I needed more of the bouncy goat and was it wrong of me to want Chomp to be fed something other than chicken??? Like a criminal or three??
I can’t wait to happen next with Cassie, the animals, and of Course Jake!
Thanks to the author for the advance copy.

[Denise Little · Rating 5 out of 5]

This is a captivating thriller from Shannon Hollinger! The characters and setting was described so well, I felt like I was right there with Cassidy, trying to solve the mystery! I love the animals in the book too. A must read!


Release date September 8, 2025

[Sherry Fundin · Rating 4 out of 5]

I have a weakness for books that have a Florida setting, especially in the Everglades. It’s not just the people that can be dangerous, so can your surroundings. So, that being said, welcome to Gator Glade and FBI Agent Cassidy Knox’s nightmare.

Cassidy had left Gator Glade in the dust, but when her grandfather dies, she returns to her home town. She is recovering from her confrontation with a serial killer. and she is the only one left to take care of her grandfather’s affairs. Will she stay? Will she be able to conquer the demons that drove her away?

Things are not as they first appear. Danger surrounds the animal sanctuary, which puts Cassidy in danger too. There is a subtle hint of menace that mounts with each page I turn and I anticipate something bad happening. We have a romance slowly developing, but characters that have baggage tend to make for complicated relationships. Will there be a happy ever after? I’m not telling.

I want to thank Shannon Hollinger for the opportunity to read and review for the first book in the Cassidy Knox series, Deadly Sanctuary.

See more at http://www.fundinmental.com

[Bella Crooke · Rating 5 out of 5]

GUYS???? THIS IS PROBABLY ONE OF THE BEST BOOKS IVE EVER READ IN MY ENTIRE LIFE?????
AHHHHHH. Shannon is a MASTER STORYTELLER🤭💜
HOW IS THIS THE FIRST BOOK IVE EVER READ BY HER????
I can’t believe I just now read a book by her.
INCREDIBLE CHARACTERS THE BIG TWIST AT THE END??? AHHHHHH MY MIND WAS BLOWN. let’s not forget the LOVE TRIANGLE🤭🤭
MASSIVE FAN OF SHANNON AND HER AS A HUMAN AND AUTHOR😭 THE SUSPENSE THROUGH OUT THE BOOK WAS WILDDDDD🤭

[Trina Dixon · Rating 4 out of 5]

Agent Cassidy Knox hasn't been back to Florida Everglades since she left over 20 years ago, but has returned to bury her Grandfather Butch. Encountering old friends, some welcome, others not so much, she wants to clear the animal sanctuary and leave as quickly as possible. On the discovery that Butch's death was not natural causes, and another town's person is killed in similar circumstances, makes her decide to stay and find out what happened.
This is a strong start to a new series, Cassidy is a strong character, she's determined not to let those who think they know best get the better of her. Some of the animals in the sanctuary stole the show, Stephano the goat was a great addition.

[Rick Molitor · Rating 4 out of 5]

This is a good thriller. Cassidy is a FBI agent on leave because of a case that included the traumatic death of her partner. She receives a call that her grandfather has died. When she returns home to the animal sanctuary where he lived, she discovers that things don't make sense. She starts to investigate. She doesn't know who, if anyone she can trust. Can she find out what is really going on? An interesting read.

[LitWithBritt27 · Rating 4 out of 5]

Shannon Hollinger’s Deadly Sanctuary is full of small town secrets and that constant, uneasy feeling that no one can be trusted. The pacing is steady in the best way, keeping me engaged without ever dragging.

Cassidy Knox is such a strong yet vulnerable lead. The way her panic attacks were written felt so real that they gave me anxiety just reading them. That emotional layer made me root for her even more.

The mystery kept me guessing, the tension never let up, and the ending wrapped things up in a way that was both satisfying and left me eager for what comes next. I’ll definitely be following Cassidy into future installments.

[Shannon Hollinger]

Dear Reader,

I am SO excited to share this new series with you! I'm in love with the characters, the animals, the setting - every little thing about it.

Of all the books I've written, this was the first that I immediately had to write a sequel. And then the third. Now that the first is ready to release and the next two are with editors, I can't wait to return to Gator Glade and start the fourth.

If you like your books twisty, with plenty of suspense, mystery, animals, intrigue, and a bit of romance, I hope you'll check out this thriller!

Thank you so much for your support!

Shannon

[Heather Flaherty · Rating 5 out of 5]

I am a huge fan of Shannon Hollinger and cannot rave enough about this book in her new series. This is definitely a must read and I cannot rave about it enough. Cassidy Knox has come home because her grandfather had died suddenly. As an FBI agent, she knows how to spot inconsistencies and to investigate, and she plans to do just that to find out what happened to her beloved grandfather. It also just happens that her first love is helping her. Can she figure it all out before she is the next target?

[Maureen ~Bitch Can Write A Book · Rating 5 out of 5]

What a ride. I really enjoyed this one. This is book 1 in the Cassidy Knox series. And I gotta tell you I’m hooked. It’s fast paced with a unique plot and great characters. I can’t wait to see where the author takes the series.

If you love crime thrillers. Add this one to your TBR. You don’t want to miss it.

[Angela Frank · Rating 5 out of 5]

Awesome book!

I love Cassidy! She is a strong main character with grit, morals, and determination, and she's just very likable! I can't wait to read what happens next in her story! When is book 2 coming out? I devoured this book! Great read!

[Michael Baldwin · Rating 5 out of 5]

Disclosure: I received this book through a Goodreads giveaway.

The book opens with main character Cassidy Yates, FBI agent, at a funeral for her partner. As narrator, Cassidy explains that her partner died saving her. At the end of the funeral, she receives a phone call that her grandfather has died, and she heads to Florida for the funeral and to handle his estate, which includes a wild animal sanctuary. However, it appears that her grandfather did not die of natural causes, as the death certificate stated, setting Cassidy on a quest to find out who killed him and why.

The incident that cost Cassidy's partner his life also left Cassidy with physical injuries and PTSD. The author does a good job of portraying PTSD. Cassidy is fine until something random triggers the memories and she freezes. She has no control over what causes the episodes and is frustrated and angry that she can't stop them. The incident is vaguely referenced mostly, because (as narrator) Cassidy is trying not to think about it, but it is revealed when Cassidy opens up to a friend about what happened.

When the killer is revealed, the reader can look back over the story and see the clues, but the clues are not so blatantly obvious that the reader would automatically know as soon as (or shortly after) the suspects are introduced.

There are a few points in the story where the reader would wonder why Cassidy takes certain actions, given her current situation [I'm not going to spoil the plot, so just imagine a horror movie character going back to check if the monster is really dead), actions that are necessary to keep the story going, but Cassidy's behavior can be easily excused by her current mental state (PTSD, survivor's guilt, grief, etc.).

I liked this book, and I plan to read the next book in the series.

[VDKeck · Rating 5 out of 5]

Murder, mosquitos, and messy secrets—welcome to the Everglades, baby. 🐊🔥

Y’all! Deadly Sanctuary by Shannon Hollinger is a swamp-soaked thrill ride that grabs you from page one. FBI Agent Cassidy Knox swore she’d never return home, but grief drags her back—and right into a fresh murder investigation that makes her question everyone. 🌫️

Old flames, blurred loyalties, and betrayals that bite harder than a gator—this book twists fast and cuts deep. The atmosphere? Sticky, buzzing, dangerous. The writing? Razor-sharp and impossible to put down.

⭐️⭐️⭐️⭐️⭐️ Knockout. Don’t read it alone in the dark. 😏🔦

[Amanda Ho · Rating 4 out of 5]

This book, is not only the first book in the series but it kept me so entertained that I just sat and read this in one sitting! It was so fun to read and also loved the whole plot. The mystery was just what I needed after reading a heavy on the smut side book as a refresh to my brain cells. (A woman has needs and must read those though as well 😉) I can’t wait until book two, too bad this isn’t even published yet, so I suspect I may be waiting a while as I won this e copy through a Goodreads giveaway!

[Rachel Browning · Rating 5 out of 5]

“Deadly Sanctuary” by Shannon Hollinger is a thrilling ride from start to finish! This story is packed with danger, lies, and deception, keeping the tension high on every page. It’s fast-paced and full of shocking twists that kept me hooked. Cassidy is a strong, determined character who has to dig deep to uncover the truth while fighting to stay alive. Hollinger weaves suspense and intrigue so well that I couldn’t put this book down. A fantastic read for fans of edge-of-your-seat thrillers!

[Melissa Anderson · Rating 5 out of 5]

Another amazing book by Shannon Hollinger! I love her writing and this book definitely did not disappoint!! Looking forward to the next book in this series, however, I would still like the last book in the Maggie Riley series.

[Emily Dickson · Rating 5 out of 5]

Great from start to finish!

Cassie is a fantastic character! Lots of twist and suspense and a great story. Loved the flow of mystery and how she dealt with her issues left from a previous case with the FBI. A little PTSD and when she returns to her home town due to the death of her grandfather she has to also take care of the animals in his sanctuary. Loved it and will be reading more by this author!

[Constance Norgaard · Rating 5 out of 5]

Deadly Sanctuary: An addictive mystery crime thriller with gripping suspense (Cassidy Knox Book 1) S

An enjoyable read. An FBI agent on leave finds her Grandfather dead from ligature marks, not a heart attack! She is shocked. An animal sanctuary that she has to save and an exboyfriend that happens to be a lawyer. This could be confusing but seems to work in her favor.

[Tammy Lunsford - Escape to Books By Tammy · Rating 5 out of 5]

When I tried to think of how to start this review, I decided that small town, big secrets summed it up pretty well.

FBI Agent Cassidy Knox has just suffered through an extremely traumatic experience on her job, which has left her with PTSD and panic attacks. Then she receives a phone call that her grandfather has passed away. Butch raised her, so he is actually more like a father than grandfather. She is devastated and still very much mentally unwell from her traumatic experience, which you will eventually learn another later in the book.

When she arrives in Gator Glade at his animal sanctuary, she thinks her visit will be short. However, those keen observation skills she learned in the FBI help her realize something is just not right. She does not believe that her grandfather died of natural causes. Something smells to high heaven in Gator Glade, and it is not the animals on the farm.

The author will keep you guessing until the final portion of the book. I knew something hinky was going on, but I could not quite put my finger on who and why. The pacing was perfect. The mystery was gritty and edgy. It was one of those that made the hair on the back of my neck stand up because I feared what would be around the next corner. Cassidy does not know who she can trust, and neither will you.

I loved seeing Cassidy grow through her struggles and become stronger.

Bravo to Shannon Hollinger for choosing such a unique setting for a fantastic mystery, as this made it even more mysterious. The descriptions of the sweet animals were just an added delight this one of kind crime thriller/mystery.

This is a dynamite first book in what I hope will be a long running series.

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

[Joanne Dunn · Rating 4 out of 5]

4.5 stars

What an explosive start to a new series!

Deadly Sanctuary introduces us to FBI Agent Cassidy Knox, who is fresh off a case that ended in tragedy, leaving her with both emotional and physical scars. As she battles PTSD and wonders what will become of her career, she is devastated by the news of her grandfather’s death- the man who raised her from childhood. Returning to Gator Glade in Florida, for his funeral, Cassidy takes responsibility for looking after the animals at the sanctuary he ran. The sight of her Grandfather Butch at his funeral, prompts suspicions about what really happened to him, unleashing a torrent of questions that quickly becomes dangerous.

Initially broken and meek, Cassidy is thrust on a journey and starts to rediscover her strong, fierce, and feisty self in a place she thought she would never return to. Here, she finds a sense of piece and of being home, realizing she is no longer alone.

The story captured my attention with its brisk pace, introducing a dynamic cast of characters-some to love, some to hate-and whet my appetite for what lies ahead for Cassidy.

[Susan · Rating 5 out of 5]

This is a great start to a series. The character of Cassidy is tough but vulnerable. Her panic attacks and mistakes make her a very human character that people can relate to. The contrast of that to her passionate defense of the animals at the sanctuary (especially the Zebra) show how fearless and tough she can be on the other side especially when she cares about something.

I really felt like you could connect to the story with this being her grandfather's home and her shared love of the animals just like her grandfather was so touching. I just love animals and the beauty of the Zebra and the funny antics of the goat pulled me right in by the heart.

The suspense side of the story was really good. I love the personal connection and that she is in a race against time and small town full of secrets much bigger than its size. I wanted to go out there and investigate right along with her.

I felt like this book stood out for its unique storyline and I loved the setting of the animal sanctuary. I can't wait to read Book Two in this series.

[Cheryl · Rating 4 out of 5]

It has been quite some time since I have read a mystery book. Yet, I do have to admit that after reading this book, I am going to have to jump back into mysteries again. For me it was the world building that really captured my attention with this book.

Shannon writes a vivid world building with this book that instantly, I was transported. It was like I was Cassidy and experiencing everything through her eyes. I love the animals that were featured in this book. They provided a nice lighthearted touch to the story.

I did find that the pacing was steady. It stayed that way throughout the whole book that I did find myself reading and keep reading. Cassidy is relatable and that I liked. It made it easier to get behind her and support her. If you are looking for your next mystery thriller, you will want to pick up this book.

[Kristina Anderson · Rating 3 out of 5]

Deadly Sanctuary by Shannon Hollinger is an intriguing thriller. The Florida Everglades is a great setting for this type of book. It is dark and dangerous plus you do not know what or who will be lurking around the next corner (or cypress tree). Cassidy Knox is a trooper. She may have taken a hard knock, but she is not down for the count. When it appears her grandfather’s death was not natural, Cassidy is determined to get answers. She wonders who she can trust. Secrets, danger, and deceit abound in this small town. There are several suspects on Cassidy’s list in this intriguing, suspenseful mystery. The whodunit will keep most readers guessing. The story had a satisfying ending. I loved Stephano the goat. The goat was a scene stealer. Deadly Sanctuary is the first book in the Cassidy Knox series, and I am eager for the next book to come out.

[Renee Simmons · Rating 5 out of 5]

When your past becomes the most important thing in your life, if you can stay alive.
FBI Agent Cassidy Knox is going through a lot of guilt from when her partner dies while trying to rescue her. But that is nothing compared to what comes next, when she receives the call that her grandfather has passed away. Now back in her hometown of Gator Glade Florida ,nothing is as it was when she left. High school friends seem to have changed, and secrets leave her wondering who she can trust. If she reveals what she discovered to the wrong person..no one involved will be safe. This book is so good and will keep you guessing. Should she stay on her grandfather’s land and fulfill his wish, or run from danger and leave it all behind to save herself

[Carol Nauss · Rating 5 out of 5]

What a terrific start to a new series. Meet Cassidy Knox a tough, resilient and totally likeable character. Cassidy resides in Virginia where she is on leave from the FBI. When she is notified about her grandfather's death from a heart attack, she heads to the Florida Everglades to settle his estate. While there, she finds that not everything is as it seems. The plot is exciting and filled with suspense. The setting of her grandfather's rescue sanctuary contributes to the mystery. This is a must read book which the reader will have a difficult time putting down. Well done, Shannon!

[Mike Lyons · Rating 5 out of 5]

Dynamite read - from the gripping first line to the last. I really enjoyed this book. I was hooked from the first line. I read it through in just 4 hours not stopping because it was riveting. I live in Florida close to where the story is set and I was able to recognize the character types and locations as being authentic. I had a good twist at the end - I didn't see it coming. I will make sure I read the next in this new series.

[Frank Lamon · Rating 5 out of 5]

O.M.G.
Shannon Hollinger has knocked it out of the ballpark with this one! From the first page til the last, I was spellbound. Follow FBI Special Agent Cassidy Knox as she searches for her grandfather's killer while not knowing who she can trust.

This could quite possibly be the best book that you read this year. I can't wait for the second installment in this series!

[Melanie Houghton · Rating 3 out of 5]

This has a great story line and all kinds of characters. Physically and mentally damaged ones, old crushes and abusive ex’s. Not to mention a killer. I felt like there were some hole in the story or maybe just not explored enough. The story is interesting enough that I will give some of the authors other books.