Killer Countdown

Stella Knox #15

by Mary Stone

One countdown. One prophecy. Zero second chances.

FBI Agent Stella Knox has faced monsters in every form—serial killers, cult leaders, and the darkest corners of the human soul. So when a millionaire’s home burns and his daughter vanishes, a ransom demand screams textbook kidnapping. Until the girl strolls into the wreckage...and murders a federal agent.

It’s not the end of a case. It’s the beginning of something far worse.

Stella’s team is left reeling. Carved into the agent’s flesh are ancient cuneiform symbols—grotesque signatures that have surfaced at ritualistic crime scenes across the country. Wisconsin. Idaho. New York. And the small Pennsylvania town where Stella thought she helped end a nightmare.

She was wrong.

The Administrator has returned. And he isn’t alone.

His disciples believe the world is ending. That salvation requires sacrifice. And unless Stella and her team can unravel the prophecy and unmask the mastermind behind it, blood will soak the streets...including the blood of those she loves most.

Killer Countdown is the explosive final book in the Stella Knox series by bestselling authors Mary Stone and Stacy O’Hare. The end begins now.

256 pages, Kindle Edition

Published June 30, 2025

About the author

To download my FREE BOOK, click here: https://authormarystone.com/free-book...

Nestled in the tranquil Blue Ridge Mountains of East Tennessee, Mary Stone has transformed her peaceful home, once bustling with her sons, into a creative haven. As her family grew, so did her writing career, evolving from childhood fears to a deep understanding of real-life villains. Her stories, centered around strong, unconventional heroines, weave themes of courage and intrigue.

Mary's journey from a solitary writer to establishing her own publishing house marks a significant evolution, showcasing her commitment to the literary world. Through her writing and publishing endeavors, she continues to captivate and inspire, honoring her lifelong fascination with the mysterious and the courageous.

Reviews

[Jacquetta Harvey · Rating 5 out of 5]

The Administrator is as always recruiting people for his cause promising them salvation if they spill someone's blood. They believe the world will end and blood will spill to cover the streets.

Millionaires daughter Tyra Scharf, kidnapped or missing from home that burned. Her father searched for her almost dying himself in the process of trying to save Tyra. Her body was not found after the fire had been put out and her car was gone. So, where was she and why was her car gone. After receiving pictures and messages of a ransom demand, the team springs to work just to witness the money drop but no one picks it up. Curios.

FBI and Police were at the burned home when the Kidnapped or missing Tyra Scharf showed back up again. The horror she unleashes at her home has made her happy and FBI officials and Police horrified. 

Will FBI SA Stella Knox and her team find the Administrator and stop the violence or will more FBI and friends be killed?

[P J Van Benthusen · Rating 5 out of 5]

Stella and Hagen thought they had solved this crime before they left Pennsylvania. But a similar crime followed them back home. They think they have solved it again only to find similar crimes popping up all over the country. The similarities are unmistaken, and the ancient symbols of a long-forgotten language are appearing on the bodies. Finally, they join forces with some of our old friends Journey Russo and Lucas Sullivan. The four agents working with others across the nation begin to narrow down the suspects. But then they uncover a plot for mass murder, and they are running out of time. Lots of twists and turns and you will be unsure who the mastermind is until the very end. Fun read and a good finish to another great series.

[Becky Russo · Rating 5 out of 5]

Stella and Hagen are making Christmas plans when an arson and kidnapping occur. While investigating the case one of their own is killed in the same fashion as the victims in the last two cases they worked on and thought solved. Now it seems like these crimes with cuneiform markings are happening in several states and apparently marks the coming of the end of the world and only those who make sacrifices (killings) will be saved. It is a race against the clock to figure out who is the "Administrator" who is leading this cult before more sacrifices are made. This book was great and I loved the characters. I will miss Stella and Hagen but love the way Ms. Stone ended this wonderful series.

[Sue Sandifer · Rating 5 out of 5]

Stella, Hagen, Ander and Alessandra have their hands full in this story. After a fire at the family home, a teenager can’t be found. She was there before the fire but when going thru the ruins she is nowhere to be found. Her body is not in the burned home. Fear is she has been kidnapped by the person or persons who set the fire. When the daughter does show up, she commits a murder that no one saw coming. She is part of a cult of doomsday folks who are sure the world is coming to an end. The race begins to find the other members of this cult group before any more people are killed. This was really good!

[Teresa Hunter · Rating 5 out of 5]

Killer Countdown ( Stella Knox FBI Mystery Series Book 15)

OMG!!!!!!!!! This book was truly amazing and totally scary. I put off reading this book because I didn't want it to end, I cried, I laughed and really had to think about how people could be talked into believing anything. This one was scary, I am going to miss Stella and Hagan, as well as the whole team. I will always wonder if Ander finds true love again, and if he comes back to fieldwork again. I am sad that this is the last book.

[Sue Palmer Crosby · Rating 5 out of 5]

Both Hagen and Stella haven’t made a decision on who with they’ll be spending the Christmas holiday. Now that their last case is over with they have some downtime coming. But is it? A phone call from Slade, their boss, sends them out to another murder mimicking the ones in Pennsylvania and Nashville earlier. Is it a copycat or has the Administrator reared their evil head again? Working closely with Sullivan & Russo, they start the hunt before the end of the world arrives.

[Shari · Rating 5 out of 5]

FBI agents Stella Knox & Hagan Yates & team are investigating a kidnapping from a burning house only to find out the clues follow the last case they were on, the cuneiforms carved into victims. Could the protagonist called toe Administrator be a professor of ancient history? A fast paced read that keeps you turning pages for a surprise ending. A bittersweet final goodbye to Stella but a great ending that won’t disappoint

[Reader · Rating 5 out of 5]

What a crescendo to the series. I could not stop reading. Stella and Hagen, joined by Journey and Lucas, race against the time to solve and stop the killings. They’ll do anything to find the administrator and prevent armagedon. The story is intense and full of surprises. Mary created another perfect ending of the amazing series. I will miss Stela. The heartbreaks and the new beginnings will stay with me forever.

[Donna Bailey · Rating 5 out of 5]

Goodbye

So sad that this series has ended but Stella and Hagen went out with a bang! This story was definitely a nail biter with all kinds of twists and turns. The book was hard to put down but I wanted to read as slow I as possible knowing it was the last and not wanting to get to the last page. I highly recommend this entire series and all the other books Mary has written. Goodbye, Stella and Hagen.

[Bonita Barbick · Rating 5 out of 5]

Mary Stone is a master at creating evil characters and along with Stacy O’Hare the villain in Killer Countdown is truly diabolical! The mystery in this novel is very complex and keeps the reader turning pages to figure it all out. Sad to say goodbye to Stella and Hagen they have certainly had very thrilling adventures. Great series!

[Marion · Rating 4 out of 5]

Will Stella and the gang be able to stop the body count and "the end of the world"? Will they figure out who the Administrator is before it is too late? Killer Countdown is a page turner that will keep you guessing until the end. Thank you, Mary Stone and Stacy O'Hare, for a great series. Will miss Stella and Hagen and all their ventures.
I am an ARC member, and this is my honest review.

[Carol Kraft · Rating 5 out of 5]

Killer Countdown is the final book in the Stella Knox series by Mary Stone and it is a great book. Stella and Hagen are tasked with finding the Administrator of a group that has an online present and are focused on killing people and leaving cuneiform symbols on their backs.

The book is full of mystery and suspense and I am sorry to see the series end.

[Linae · Rating 4 out of 5]

The End. Gone not forgotten

Another excellent series completed. This last book was full of intrigue like the books that came first. I really liked that characters from another series of Mary's came together for the finale. I wish we had just one more book with everyone but this is a good ending to a memorable series.

[Sammye · Rating 4 out of 5]

This is the fifteenth book in the Stella Knox series. Just as all the others, it’s an excellent thriller. Stella and her team are investigating a kidnapping. But is it really. The twists and suspense kept me on my toes! Another enjoyable series episode.

[Meriah Gutterson · Rating 3 out of 5]

good, but....

The book, the plot, the story, and the characters were all amazing, as always.

However, I feel that this one could've been much better, and a cleaner read, with an editor. So many mistakes!

[Patricia Sherman · Rating 5 out of 5]

Great book

This series has truly been exciting. The cases just kept getting more exciting ,and crazier. People they love died but in the end they get their killer. If you want a great series read these books.

[Dale Francis · Rating 5 out of 5]

Great Book Great Series

I read every one of the books in the Stella Knox series. Every one of them was an amazing adventure. This last book, Killer Countdown, was a thriller from start to finish. Thank you Mary Stone. I'm ready to start on your new book.

[Sandra Harlow · Rating 5 out of 5]

Great series

I'd recommend this book and the entire series to fans of crime, drama and relationships. The characters are well defined and you cheer them on as well as feeling the heartbreak of losing one.

[Patricia A. Biba · Rating 5 out of 5]

Who Was The Administrator?

This story was a cliff hanger. The reason for the deaths and the solving of who was responsible. The mystery wasn't known until the very end. Good reading and an excellent story.

[Eleanor Andersen · Rating 5 out of 5]

WOW this is an extremely good book. I couldn't put it down. An edge of the seat page turner.

[Robin Mattei · Rating 5 out of 5]

excellent addition to the series. So sad its ending

[Carol Dickens · Rating 5 out of 5]

Killer Countdown

I know this is supposed to be the end of Stella, but I hope she will pop up now and then. I have truly enjoyed every one of the books in this series.

[Barbara Kaake · Rating 5 out of 5]

This was a excellent story about Stella and team fighting evil and finding out who is responsible with lots of suspense and action . Thank you.

[nina · Rating 4 out of 5]

sad to see the series come to an end🥲🥲

[Anne Regula · Rating 5 out of 5]

Totally Awesome

Another super great read by my favorite author! I love the way the storyline keeps tasking different turns and twists! Great read from beginning to the end!

[Angel Hite · Rating 5 out of 5]

AMAZING

Best one yet!! I laughed. I cried more than once. Can’t wait for the next Stella book! I loved it. Couldn’t put it down!

[Helen · Rating 5 out of 5]

Brilliant!

Just thoroughly enjoyed this series. Would recommend. Pity this one had to end. The whole team was great, particularly Stella and Hagan.

[Susan · Rating 4 out of 5]

Why 4 stars? Because it's just so darned sad.

[Kathy Cooper · Rating 5 out of 5]

loved the series

I loved being invited into the life of Stella and Hagen. Very good book!! If you’re looking for a page turner this is the book for you!

[Alicia · Rating 5 out of 5]

Spoiler Alert! There's a sweet character surprise in the book that I love love love and I hope they have the opposite surprise in the future. An excellent end to the series.