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Cold Case K-9

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Only a competent K9 and her handler could find her sister’s killer.


CBI Agent Gabriella Ruiz is convinced a missing hiker is a reemerging serial killer’s next victim. Believing she’s too close to the case, the Bureau refuses to follow her hunch. Luckily, Gabriella finds unexpected help in Crooked Pass Security’s unique investigative team. Expert tracker Diego Rodriguez and his faithful K-9, Poppy, go searching for clues from the ground up. But when the killer focuses on Gabriella, Diego — and Poppy — must keep her safe from the killer’s dangerous grasp.



Mills & Boon Intrigue — Seek thrills. Solve crimes. Justice served.

Kindle Edition

Published January 1, 2026

12 people are currently reading
22 people want to read

About the author

Caridad Piñeiro

191 books1,135 followers
Caridad Pineiro is a transplanted Long Island girl who has fallen in love with the Jersey Shore. When Caridad isn’t taking long strolls along the boardwalk, she’s also a NY Times and USA Today bestselling author with over a million romance novels sold worldwide. Caridad is passionate about writing and helping others explore and develop their skills as writers. She is a founding member of the Liberty States Fiction Writers and has presented workshops at the RT Book Club Convention, Romance Writers of America National Conference as well as various writing organizations throughout the country. You can connect with Caridad at www.caridad.com. You can also find Caridad on:

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5 stars
33 (52%)
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21 (33%)
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8 (12%)
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Displaying 1 - 25 of 25 reviews
Profile Image for Donne.
1,593 reviews118 followers
December 19, 2025
I am such a sucker for a great K9 detective team story. I’m already an avid fan of several and can’t resist adding more of them to my to-read list, sometimes without even checking out more about the series, which is what happened here. I requested this ARC before realizing that it’s the third installment of the series. Anyone who reads enough of my reviews knows that I tend to be a bit fussy and a bit of a stickler about starting series from the beginning. I hate thinking that I am missing some much-needed character development in order to be able to connect to the MC’s.

As a character driven reader, character development is the most important aspect of a story, at least to me. I am not a fan of unlikeable MC’s and need to connect to a character in order to root for them. Well, fortunately, this is one of those series where every installment focuses on a different character in a circle of friends/colleagues, so there probably wasn’t a lot of development for the MC’s in this installment. Unfortunately, there were spoilers in this installment for the storylines in previous installments.

The book summary basically just introduces the primary storyline. This is a romantic suspense storyline and while I have no problem with some romance in my crime thriller/suspense stories, I prefer the story to lean more heavily on the thriller/suspense story and not the romance story. This story leans more on the latter than the former and the cover of Poppy is kind of misleading. Poppy has very little space in the story and more often is just basically arm candy or a prop.

The character development for the MC’s was good and the pacing steady to fast (second half). The storyline of the investigation of the murders was kind of predictable; I guessed the murderer almost as soon as he was introduced. For me, the writing was a combination of ok and disappointing for reasons I’ve already stated. I’m looking at an overall rating of 2.9 that I will be rounding up to a 3star review. I’m looking like an outlier on this one and I attribute it to the fact that I am a big fan of K9 detective duos and prefer stories where the K9 has a more integral role and space in the story. That and, once again, for romantic suspense stories, I prefer stories that lean more on the suspense and less on the romance. I want to thank NetGalley and Harlequin Audio, for sending me this eARC in exchange for my honest review.

#NetGalley #HarlequinAudio #ColdCaseK9
Profile Image for Madison Warner Fairbanks.
3,561 reviews504 followers
December 30, 2025
Cold Case K-9 by Caridad Pineiro
Crooked Pass Security series #3. Harlequin Intrigue category. Diverse Romantic suspense. Spin off from multiple South Beach Security series. Can be read as a standalone.
Agent Gabriella Ruiz believes her missing sister was the victim of a serial killer. A new team is added, Diego Rodriguez and his K-9 tracker Poppy. Together the three follow the clues and scents to find a killer.

🎧 I listened to an audiobook of this story narrated by Victoria Villareal. The performance is distinctive for the male and female characters with the stress, worry and desperation heard clearly. The acting held my attention throughout.
I listened at 1.5 and slightly higher to match regional conversations.

Fast moving action as the search is on for a serial killer and the reader knows the current victim is still alive and holding on.
The dog’s commands and trained reactions were interesting while the tension was ramped up every time we had a short glimpse of the current victim.
Being in the head of the killer is chilling.

I received a copy of this from NetGalley and publisher Harlequin Audio, HarperCollins
I purchased multiple formats to keep and revisit.
Profile Image for Carla.
7,840 reviews183 followers
February 27, 2026
Cold Case K-9 is the third book in the Crooked Pass Security series, but I had no problems following the story. A hiker is missing in the mountains of Colorado and GBI agent, Gabriella Ruiz is convinced it is a serial killer who was active a few years ago. No one at the bureau believes her, but tracker Diego Rodriguez with his K-9 Poppy offers to help. Together they follow the clues to track a killer, that has his eyes on his next victim, Gabriella.

I enjoyed this story, but would have liked more Poppy in the story. This story has lots of twists, and suspense. The kidnapped victim is still alive and we see her often in the story. I didn't know if they would find her before she was killed, and that aspect kept me listening whenever I had a few moments. The story moved quickly as the search went on, with lots of action. We got the killer's POV and that was chilling, especially when you realize he wants Gabriella. This is a serial killer story, so there is talk of other victims and one in particular, Gabriella's sister. Overall, I enjoyed this story a lot, with action, suspense, some twists, and some romance. The audiobook was narrated by Victoria Villareal and she does a great job. She had the accents and voices down pat and added to my enjoyment of the story, pulling me in right from the start.
Profile Image for Nancy.
2,604 reviews64 followers
January 13, 2026
Lots of serial killer facts which were enlightening but I skipped most of the serial killer “head” scenes.
AI prominent in this one.
Profile Image for Heather.
327 reviews
February 11, 2026
I don't quite know how to review this book - it started off so strong and then threw in a couple hard declines.

🎧 Firstly, the narration by Victoria Villareal was perfect for this type of story - I loved her FMC & MMC voices and general tone. 5⭐️

📚 Story-wise, I'm always intrigued when there's POV's from the killer/suspects perspective. Plus I will usually add it to my reread shelf so I can see how the clues were there from the beginning. I feel like in a short period of time, we got to know both MC's pretty well. I didn't read the previous two books in the series, which probably helps flush out secondary characters, but was not needed to follow this one.

📍The phrase "stick with you like white on rice" should never be used - I've only ever heard it used in racist connotations. When this phrase was read, I was completely taken out of the book and given a major ick feelings, even more-so because the phrase didn't seem to fit the character at all. And then it was used AGAIN (I know it's probably too late but please consider putting another phrase here). I do want to say, that I don't think the author intended any negative meaning, just might not be aware of it being a more regional slur. Up UNTIL THIS POINT, I would have rated this book at 4.5 ⭐️.

Towards the end, some of the 'declaration of love' dialogue made me cringe a bit, but it wrapped their HEA up quickly in a little bow.

➡️ I'm going to wait before I post my review on public platforms - I'd like to see how this sits and if anything changes. I've saved it as a draft but idk.
Profile Image for Susan.
215 reviews11 followers
February 24, 2026
This was a great suspense story. I was fortunate to experience the audiobook version and I found the narrator's distinctions between male and female voices to be done very well. She did a great job portraying the emotions behind the words.

I love that this book reads like a K-9 novel that meets criminal profiling. These are both favorites of mine so to see them in the same book was a good read for me. I feel like people who love profiling shows will be very much drawn to this one.

I loved Poppy and that this had a GSD as the K-9. I wish that Poppy had an even bigger role with a little more personality since the cover has the dog front and center. I love the cover art and was instantly drawn to it because of the prominently featured dog. I love when the dog is mentioned on most pages like a partner who is an extension of an officer.

I enjoyed the serial killer aspect of the story and the insight into their mind. The suspense and the action were well done and kept me listening in anticipation of how it would all turn out. I enjoyed the romance and the twists and turns of the story and the style of the author. This pulled me right in from the start and I am very much looking forward to reading and listening to more work from this author and others in this series.

Thank you to Netgalley, Harlequin Audio and HarperCollins for the opportunity to read and review a free copy of this book.
Profile Image for Nikki.
1,211 reviews31 followers
April 11, 2026
Gripping romantic suspense with a heroic K-9 that stole the show!

Caridad Piñeiro delivers another winner with Cold Case K-9! CBI Agent Gabriella Ruiz is determined to stop a reemerging serial killer, especially when she suspects the latest missing hiker is connected to her own sister’s cold case. Teamed up with expert tracker Diego Rodriguez and his amazing K-9 partner Poppy, the story explodes with tension, danger, and high-stakes action from the very first chapter.

I was completely hooked by the fast-paced plot, the emotional layers (especially Gabriella’s personal connection to the case), and the sizzling chemistry between Gabriella and Diego. Poppy isn’t just a side character—she’s a true hero with incredible tracking skills and heartwarming moments that make the story even more engaging. The blend of intense suspense, tender romance, and faith in justice kept me listening straight through.

Narrator Victoria Villareal does an outstanding job bringing every character to life. Her pacing during the action scenes is perfect, and she captures the emotional depth and urgency beautifully. At just over 6 hours, it’s the ideal length for a thrilling escape.

If you love romantic suspense with strong heroes, smart heroines, and unforgettable K-9 partners, this audiobook is a must-listen. I couldn’t stop recommending it—definitely one of my favorite listens this year!

3,626 reviews41 followers
December 18, 2025
This audiobook engages the listener from beginning to end.
CBI Agent Gabriella Ruiz has never forgotten her younger sister who was believed to have been abducted and never found. Now that a young woman has disappeared, Gabriella is certain that a serial killer is at fault and possibly the same person that took her sister.
Her team believes she’s putting her feelings first, but not the Crooked Pass Security. One of the members of the group is Diego Rodriguez. Diego , with his K-9 Poppy, is willing to help her.
As the two start digging into the cold case, and the potentially current missing woman, and the danger that surrounds them, feelings develop.
Will they be able to find the young woman that’s missing? Will they be able to finally stop the serial killer? Is he the same person that took Gabriella’s sister? And, in the end, will they find their HEA?
The story was engaging and the main characters likable and well developed.
The narrator, Victoria Villareal, brings the story to life.
I was entrusted a copy of this audiobook by Netgalley and Harlequin Audio. The opinions expressed are solely my own.
Profile Image for Hope.
421 reviews2 followers
January 1, 2026
Gabriella Ruiz is convinced she's on the trail of a serial killer, even if no one else does. Luckily, K9 handler Diego Rodriguez is willing to follow her gut, especially when there's the life of a missing hiker on the line.

This is definitely more intense than the previous two books, where we get the POV of a pretty depraved killer. I usually steer clear of serial killer mysteries, but I've enjoyed Caridad's other mysteries and this was no exception. I kept guessing who the killer was, though it was obvious to me before it was to our leads because they have to follow procedures and stuff.

The romance also was cute. Gabriella has guilt over her little sister's disappearance and Diego suffers from survivor's guilt and PTSD. I appreciated they were open with each other and that they kept struggling and while having someone to lean on helps, it didn't "cure" them.

Victoria Villareal did an excellent job as the narrator. She kept me engaged in the story and had enough distinction between characters to keep them apart. I will check out more of her narrated books in the future.

Thank you to NetGalley and Harlequin Audio for the review copy.
Profile Image for Jessica .
124 reviews
December 29, 2025
Cold Case K9 was a solid, enjoyable listen, and I really liked it in audiobook format. The pacing worked well for audio, the story was easy to follow, and the suspense elements kept me engaged the whole way through.

I didn’t realize going in that this was part of a series, and while I don’t think I was missing anything major plot-wise, it did feel a bit like I’d jumped into the middle of a romance—especially with the MCs already clearly in love. That said, it didn’t take away from my enjoyment of the mystery or the emotional stakes, and I was able to settle into the story pretty quickly.

This is a very short book, and that was really my biggest complaint. The concept and characters easily could have supported a longer, more developed story, especially when it came to deepening the investigation and the relationships.

Overall, this was a good, fast-paced read/listen with likable characters and a compelling premise. I enjoyed it enough that I’ll definitely be checking out the rest of the series.
Profile Image for Stephanie Herron.
784 reviews10 followers
December 19, 2025
Gabriella is convinced that the newest missing person is related to her sister's case. Her partner is not as sure but Crooked Pass Security's newest hire Diego is up for the challenge. Diego works with his k9 Poppy to help Gabriella and the FBI find the missing woman. There is a really good mix of suspense and romance in the story. A majority of the story is about finding who is kidnapping and killing women. They use both the FBI and the security company resources as they race against time. Of course, K9 Poppy helps to save the day, which is important to the dog lovers reading. The ending is a little complex as it has you thinking of what justice really means to you. I did listen to the audio and really enjoyed the narrator. I realize I sound like a child, but I like to have different voices for the different characters and this did. I look forward to listening or reading more from this author.
Profile Image for Denise Schenk.
1,097 reviews14 followers
December 31, 2025
CBI Agent Gabriella Ruiz is working a missing hiker case. She has the theme that there is a serial killer taking hikers and killing them. Gabriella finds unexpected help in Crooked Pass Security’s unique investigative team. As works the case it seems that she is right about the serial killer. The new missing woman needs to be found and expert tracker Diego Rodriguez and his faithful K-9, Poppy are helping with the investigation. The leads keep going back to the same family and they are now being taunted by the serial killer. It seems that Gabriella sister went missing years ago and could be his first victim. Great story of cat and mouse.
Profile Image for Amy Avila.
57 reviews
December 23, 2025

What a wild and fast paced ride. Gabriella is investigating a new missing persons case. She thinks it might be connected to her sister. Her partner Diego wants to look at all angles. There’s tension, a K-9 named poppy, and a romance subplot. What’s not to love?

I did wish poppy played a bigger role but that’s probably a “me thing”.

I would recommend this series to anyone who likes thrillers or mysteries.

*I got this as a free ARC through NetGalley for an honest review thank you to everyone who made this happen*
172 reviews
December 11, 2025
Thank you Net Gallery and Harlequin Audio for the ALC!
4/5 stars for me.
This was a great quick read, I would have really enjoyed it if it was a bit longer.
Such as more information and back story on our MMC and FMC, and our bad guy.
Their stories felt rushed, and there was potential to add more. The crime aspect of the book was also great, but would have liked more information on the victims and the main victim of the book. Overall a great read and would love to have more to read!
Profile Image for Bookstabritni.
364 reviews
December 12, 2025
Spice Rating:🌶️🌶️

This is my first book by this author but definitely not my last! You do not need to read the previous books in the series to enjoy this one. There is plenty of suspense, mystery, and romance in this book. I appreciated that there were minimal details given from the killer’s POV so there was nothing overly disturbing. I enjoy darker suspense novels, but nothing overly graphic. The romance was low angst and did not take away from the suspense, which I considered to be the main plot.

💋 Kisses Only
🫑-🫑🫑🫑 Steamy/Closed Door
🌶️-🌶️🌶️🌶️🌶️🌶️ Spicy/Open Door
Profile Image for booksy.tx.ana.
879 reviews9 followers
Review of advance copy received from Netgalley
December 15, 2025
A suspenseful romance.
This is right up my alley. I just love these kinds of books. This certainly didn’t let me down. Gabriella and Diego are working to find a suspected serial killer. It had just enough mystery and romance. They were brought together by the situation but were also able to get to know each other on a deeper level. I’d absolutely read more.
Profile Image for Linda Shantz.
Author 17 books56 followers
Review of advance copy received from Netgalley
December 17, 2025
This was my first time for this author, and I'll definitely be looking out for more from her. I loved the weaving of new technology into old-school investigation. The romance was low-key enough not to overshadow the plot, and the dog played a sensible role. I listened to the audiobook, and the narrator did a great job.

Thanks NetGalley for the opportunity to review.
Profile Image for Daria Kushner.
312 reviews
December 22, 2025
It is a great romantic suspense with very strong and captivating plot and some elements of romance! I love the story line, the attention to details of the unraveling of the mystery step by step. Audio narration done by Victoria Villareal is great. Please note that the book is written in 3rd person but it doesn’t change the fact of how great it is.
1,831 reviews7 followers
December 9, 2025
An intense cold case that turns into a hunt for a serial killer! A fast paced suspense not to be missed! The narrator did a fantastic job bringing this story to life!

I received an audio ARC through Netgalley and all opinions are my own.
518 reviews2 followers
March 7, 2026
Well paced book with multiple possible suspects. I would have liked to learn a bit more about Diego’s past. The romance was fast but that’s common in these books. Poppy is great but I was surprised by the use of a down to alert to scent.
Profile Image for Kim Garrow.
583 reviews5 followers
January 12, 2026
I did not realize this was part of a series, but it listened well as a standalone. This was also my first book by this author, and I liked her style and will look into other writings by her.

This was a solid, romantic suspense audio. The narrator did a nice job capturing the feel of each character whether male or female. The storyline is kind of dark, centering around a serial killer. It is not overly graphic but still disturbing all the same. Our main couple, Gabriella, and Diego, have intense backstories, and I enjoyed their interaction and growing relationship. The K-9, Poppy, gave another interesting layer, but was kind of an accessory and not a main "character."

I will definitely take a look at the rest of this series.

4 stars
Profile Image for Donna.
4,162 reviews57 followers
January 3, 2026
An intriguing mystery from page 1. The author has you feeling for these characters right from the start. Diego and Poppy being bored. Gabriella’s strength and smarts. This book grabbed me and wouldn’t let me go till long after the last page.
Profile Image for Tina Loves To Read.
3,675 reviews1 follower
Review of advance copy received from Netgalley
January 21, 2026
This is a Romantic Suspense, and this is the third book in the Crooked Pass Security series. I read this book by listening to the audiobook for this book, and I really enjoyed the audiobook for this book. I got pulled into this story right away, and I did not want to put this book down. I loved the characters in this book. There was a good mix of Romance and Suspense/Action. I really enjoyed reading this book. I received an ARC of this book. This review is my own honest opinion about the book like all my reviews are.
Displaying 1 - 25 of 25 reviews