The Perfect Replacement

Thistler Thrillers #3

by Ava Roberts

Her daughter vanished without a trace, and everyone with the skills to find her has something to hide.

Three years of peaceful co-parenting convinced Finley that Calvin had finally changed. Then he married Willa.

Beautiful, devoted, and strangely eager to bond with Finley's daughter Campbell—Willa seems too good to be true. When Calvin starts pushing for extended custody and overseas trips, Finley's maternal instincts scream danger. But is the threat coming from Calvin, or from the woman who's replaced her in every way?

Then Campbell vanishes during a shopping trip with Willa.

Security cameras fail. Ransom demands arrive from untraceable sources. Someone with sophisticated tech skills is orchestrating everything—but who? Finley finds herself caught between her AI ex-husband's unlimited resources and his new wife's perfect facade, unable to trust either.

Every hour Campbell remains missing, the technology that was supposed to protect them becomes another weapon turned against Finley. Someone is always watching, always one step ahead—and Finley is running out of time to discover who's pulling the strings before her daughter disappears forever.

Perfect for fans of Jeneva Rose and Freida McFadden, The Perfect Replacement will keep you guessing until the final page—and leave you questioning everything you thought you knew.

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283 pages, Kindle Edition

Published January 6, 2026

About the author

Ava Roberts is a clinical psychologist turned author who knows that the most unsettling things often lurk just beneath the surface. She is the author of The Vanishing Neighbor, Juniper Isle, the Thistler Thrillers series, and The Summer House Murder (2026). Kirkus Reviews called The Summer House Murder “a whirlwind domestic thriller that’s also a pitiless anatomy of the costs of motherhood and sisterhood.” She lives in Massachusetts with her husband, two kids, and an overactive imagination.

Reviews

[Tonya · Rating 5 out of 5]

This third installment of the Thistler Series is suspenseful, clever and entertaining. I enjoyed being once again plunged into Finley’s complicated life. The story is emotional, compelling and had me on the edge of my seat. The pacing is perfect and kept me engaged from start to finish. I hope this is fiction and not a cautionary tale foreshadowing the future. Ingenious storytelling! I enjoyed every minute.

[Jannelies (living between hope and fear) · Rating 4 out of 5]

The third (and final?) book in this series revolving around Fiona, who creates the perfect boyfriend for herself. With devastating consequences.

I liked it that Fiona actually has grown to the woman she is in this third book. In the first book, I found her a typical teenager at 16, too young to oversee the consequences of what she did. In the second book in the series she actually goes back to college to become a teacher. A profession Calvin approves of, but even more, a way to an eventual escape from him.
I ended my review of the second book by saying the both the first and second book lacked maturity. Well, I won’t say the third book is a great deal better than the first two books but it earned a star more, mainly because of Fiona’s growth and the ending.
Fiona now has to deal not only with Finley but also with Willa. Calvin married Willa on a whim, mainly because Willa is in certain ways to alike to Fiona (and Finley of course). And although Calvin and Fiona have been co-parenting Campbell in good harmony, as soon as Willa enters Fiona’s and Campells’ lives there is something ‘off’.

There are secrets and more secrets, but the things that Fiona wants to keep secret for Calvin are almost impossible to keep secret because he is still Calvin, almost omnipotent and still very eager to rule over the women in his life.

It is a very creepy story because Calvin is now so much like other husbands who cannot take no for an answer, who make life hell for their wives. As said, Fiona is now a much deeper character and the ending is very fitting.

Thanks to Severn River Publishing and Edelweiss for this review copy.

[Pamela · Rating 4 out of 5]

I would like to thank Severn River Publishing and Ava Roberts for a digital copy of this book in exchange for my honest review.

3,5⭐ - after reading the first 2 books in Thistler Thrillers, I was eager to find out what's next for Finley and Calvin.

The story takes place 3 years after the second book. Finley and Calvin are co-parenting their 3 year old daughter, Campbell. Calvin quickly falls in love with Willa and makes all sorts of plans for their marriage and honeymoon however something seems off about Willa. She doesn't seem to mind that Calvin is AI and is eager to spend some time with Campbell.

After a shopping trip with Willa, Campbell soon goes missing. She's nowhere to be found and all cameras in the mall seem to be wiped. What happened to Campbell? Why was she taken and is Finley right to distrust Willa is she behind the kidnapping of Campbell?

The Perfect Replacement is less AI forward than the first 2 books in the series, but equally as entertaining with loads of twists. Although Calvin is AI, he develops some actual feelings towards the disappearance of his daughter. I can't wait to read book 4!

[Mary Polzella · Rating 3 out of 5]

Three years of peaceful co-parenting has convinced Finley that her ex Calvin has changed. When he marries Willa, it seems she is almost too eager to bond with Finley's daughter Campbell. When Calvin starts pushing for extended custody and overseas trips, Finley's maternal instincts scream danger. But is the threat coming from Calvin, or from the woman who's replaced her in every way?

When Campbell vanishes during a shopping trip with Willa, ransom demands arrive from untraceable sources. It would seem someone with sophisticated tech skills is orchestrating everything. Finley finds herself caught between her AI ex-husband's unlimited resources and his new wife's perfect facade, unable to trust either. Every hour Campbell remains missing, the technology that was supposed to protect them becomes another weapon used to stop Finley from finding her daughter.

This book is the 3rd in a series about Calvin and Finley, although it could easily be read as a standalone. It's quite an unusual read, with a few twists and interesting (and slightly suspicious) characters to keep the reader engaged and wondering what is really going on. The tension between the characters is taut and the central mystery around the missing child is every parent's nightmare. The AI component of the plot adds a unique sci-fi dimension to this domestic thriller and I will definitely be reading books 1 and 2 after enjoying this one . ⭐⭐⭐.5

[Heather Flores]

The Perfect Replacement by Ava Roberts is a razor-sharp, bingeable thriller that grabbed me from page one and never let go. I received an ARC from the publisher through Edelweiss, and I am so glad I picked it up. I actually didn’t realize it was the third book in a series until I finished, which says a lot about how well it stands on its own. It’s completely readable as a standalone, but I found myself wishing I already knew more of the backstory because I was so invested in these characters.

Finley’s situation as a divorced mom co-parenting with her ex, Calvin, felt painfully believable, and the introduction of his new wife, Willa, adds exactly the right level of unease. The dynamic between the three adults is tense, layered, and messy in all the best ways. I loved how the book plays with the question of who can really be trusted - Calvin, with all his resources and charm, or Willa, who is almost too perfect and eager to slide into Finley’s place. That uncertainty kept me second-guessing everyone’s motives.

I was also surprisingly conflicted about which couple I was rooting for: part of me wanted to see Finley and Calvin find their way back to each other, and part of me desperately wanted Finley to move on and claim her own happiness.

The central mystery—Finley’s daughter Campbell disappearing on a shopping trip with Willa—is both terrifying and addictive to follow. I flew through the pages needing to know what happened and who was actually pulling the strings. The use of technology and surveillance adds a chilling, modern edge to the story, making it feel uncomfortably plausible. Every time Finley tries to get a step ahead, it feels like someone is already watching and staying just out of reach.

I had so many conflicting emotions while reading: sympathy, anger, suspicion, heartbreak. I was dying to know how Calvin “became” who he is in this story and what his and Finley’s past really looked like. Even though I wanted more of that origin story, the lack of it never made the book less enjoyable—if anything, it made me even more eager to go back, read the first two books, and then revisit this one with that extra context.

Overall, The Perfect Replacement is a twisty, emotionally charged thriller that delivers on both suspense and heart. I’m giving it 5 stars and fully intend to read the earlier books in the series.

[Melissa (honeybee.reads) · Rating 4 out of 5]

The Perfect Replacement is book 3 in the Thistler Thrillers series and for full comprehension of the story and characters I highly recommend reading these in order. If you don't you'll get spoilers for book 1 and 2. This installment was filled with suspense and action. Once the plot started to unfold I was so invested. There are so many secrets to uncover and lies to bring to light. I really liked the plot in this one and how the author constructed it. It was so well planned out and once all the pieces started fitting together it just made so much sense. I was shocked and wasn't expecting what came of it.

Overall, this was definitely a good add on to the series, I am very excited to read book 4 now with that ending and see how it will all end! I am really enjoying these AI type thrillers, but they're also super scary.

✨️ Thank you to @avaroberts for my gifted ARC in exchange for an honest review.

[Sandy · Rating 5 out of 5]

The best of this series, so far! The story moves swiftly, with somewhat less AI than the previous books. The characters are very well developed, and the premise and plot are intriguing. I enjoyed this book and am looking forward to the sequel. I received a complimentary copy of this book and chose to write a voluntary, unbiased review.

[Thriller Bookie · Rating 5 out of 5]

The Perfect Replacement takes the Thistler Thrillers series to another level, combining intense suspense with questions about trust, technology, and control. I loved how this book made me think about the influence of AI on our lives without trying to convince me that the story itself is already reality.

Compelling, unsettling, and impossible to put down. This series just keeps getting better.

[LoveMyAuthors · Rating 2 out of 5]

Wow...the ex is actually an AI...just weird, not my cup of tea
Unfortunately I didn't realize this was the third book in the series and felt a bit "out of the loop" with the goings on. It made it extremely difficult to follow the emotions of the story and I just couldn't get into the strangeness of the characters being "made."

I'll be more careful with my selections going forward.

[Jackie · Rating 5 out of 5]

What an incredible book. Full of suspense and secrets. Has Calvin really changed or is that an illusion. Their daughter disappears and she needs to get it solved before anything happens to her. Don’t miss out once it’s published.

[Kenneth Lingenfelter · Rating 4 out of 5]

Calvin and Finley are divorced with a daughter Campbell. Calvin decides to find a new wife who takes Campbell shopping only to find she is missing from the store. The cameras were disabled and Campbell is gone without a trace. A page turner that keeps you guessing.

[Brittany Paige · Rating 5 out of 5]

I can’t wait for the next book! Love this series! Quick & easy to read

[Miguelina Guzman · Rating 4 out of 5]

Outstanding

I read this in one sitting looking forward reading next installation of this book will he find his daughter and the women he loved

[Linda · Rating 5 out of 5]

So good. So many twists and turns. Can’t wait for the 4th book!