Sinister Summer

by Karen Ann Hopkins

A baffling saga of mass delusion brings Sheriff Serenity Adams to West Virginia on her very first case as an FBI Special Agent. While Serenity is in unfamiliar territory, she’s introduced to an Old Order Amish community where surprises lurk around every corner. What Serenity discovers in the rugged settlement is far worse than she could ever have imagined. As she digs deeper into the past of a group of people who prioritize humility and obedience over independence, she uncovers a shocking pattern of violence across several states, spanning decades. Serenity isn’t alone in this dangerous quest to unravel the truth. She’s joined by Mallory Miller, an independent journalist, who just so happens to have grown up Amish. Startling evidence takes the duo on a chaotic journey to solve one of Serenity’s most unsettling cases yet.

Sinister Summer is a thrilling, tense, and twisty story about the power of collective persuasion. The shocking ending will stay with you long after you read the final page.

Kindle Edition

Published December 9, 2025

About the author

You can visit Karen Ann Hopkins at her website: www.karenannhopkinsfiction.com.

"I loved joining Rose and Noah during their journey in the Temptation series by Karen Hopkins."-Katie McGarry, acclaimed YA author

Karen Ann Hopkins resides in northern Kentucky with her family on a farm that boasts a menagerie of horses, goats, sheep, peacocks, chickens, ducks, rabbits, pigs, dogs, and cats. Karen rescues and fosters a variety of pets and farm animals, but she also finds time to give riding lessons, coach a youth equestrian drill team, and of course, write. She was inspired to create her first book, Temptation, by the Amish community she lives in. The experiential knowledge she gained through her interactions with her neighbors drove her to create the story of the star-crossed lovers, Rose and Noah.

Karen grew up about a mile from Lake Ontario in Upstate New York. She was bitten by the horse bug at the age of five, and after diligently taking riding lessons for several years, she was rewarded with her first horse at the age of eleven. The feisty horse's name was Lady, a Quarter Horse-Thoroughbred cross, who became Karen's steadfast companion. Through the years, the constant force in her life was horses. Eventually, Karen found her place as a riding instructor herself. Before accepting her fate in the barnyard, she worked a short stint as a paralegal, traveled abroad, and guided tourists on horseback riding tours in the Smoky Mountains of Tennessee.

Karen is currently working on her two interconnecting mystery/crime fiction series, Serenity's Plain Secrets and Possum Gap, along with several new projects.

To learn more about Karen and her books, please visit her website.

Reviews

[Tee loves Kyle Jacobson · Rating 5 out of 5]

This is the first book I have read by Karen Ann Hopkins and it won't be the last. I could not get enough of this story. It had suspense and mystery in it and the world of Amish. I really loved how the author described the Amish and how they live. The Amish are a very interesting group of people that I love to read about. They live such simple lives and stay together no matter what happens. They are a secret society that lives off of the land.

Sherriff Serenity Adams is a Sherriff and has just become an FBI Agent. Her first case is to investigate the deaths of an Amish family. At first she is leery about investigating the case but her husband and her Deputy both tell her to go and do her job. When she arrives at the colony she is greeted by a women that has snuck up on her. As she talks to the women she gets some information about the deaths of the family and she starts to think there is more to the story that she is being told. Then when she goes to interview one of the woman in the colony she meets another woman who wants to help her out with her investigation.

As the two woman work together to find out what really happen they are shocked by what they find out. They must work together to catch the killer. That is where the mystery begins because they must figure out the puzzle before another death happens. As they work together they figure out who the killer is and why he is targeting the Amish. What unfolds is an amazing story that will have you on the edge of your seat reading faster to find out what is happening and why.

[Maria Baker · Rating 5 out of 5]

Sinister Summer is one of those rare thrillers that grabs your attention before it’s even published, and somehow still exceeds expectations. Karen Ann Hopkins blends FBI procedural tension with the haunting quiet of an Old Order Amish community, delivering a story that feels both deeply atmospheric and relentlessly suspenseful.

Sheriff turned FBI agent Serenity Adams is immediately compelling: sharp, steady, and completely out of her element as she steps into a world where silence, obedience, and tradition run deeper than any official investigation. The partnership with Mallory Miller, whose own childhood among the Amish adds emotional weight and insider insight, creates a gripping dynamic that grounds the novel’s escalating mystery.

What makes this upcoming release so chilling is how Hopkins handles collective persuasion and the slow burn of hidden violence across decades. The clues unfold with precision, each revelation more disturbing than the last. Even without the final version in hand, the narrative promises a shocking conclusion that lingers long after the last page.

Readers who enjoy atmospheric thrillers, Amish-country mysteries, or psychological suspense with real emotional depth will want to keep Sinister Summer on their radar. This is shaping up to be one of Hopkins’ most unsettling, and unforgettable, novels yet.

[Rachel Boyd · Rating 4 out of 5]

New to the series and I'm going to have to go back and read the rest! This book was the kind you read in a day. This series has a female main character, Serenity, who is a sheriff and has occasional jobs with the FBI. Her specialty is dealing with Amish populations, which is so interesting to me. When a family passes away, things feel off and Serenity looks into what happened. In a closed off community, like the Amish, answers are hard to come by.

There are some great characters in this book. I really enjoyed Saretta; she was a cool lady and kind. Mallory really added to the story in a way I wasn't expecting. When I was reading, I suspected I had solved the 'what happened' aspect, and I did. BUT, the entire reasoning behind how that played out was not expected. The story was really good with an interesting motive. Definitely an unusual ending, but I enjoyed that.

I received an advanced copy and am leaving a review voluntarily.

[Author · Rating 5 out of 5]

Sinister Summer by Karen Ann Hopkins is a truly gripping thriller of a story with a plethora of facets ranging from cultural differences, criminal intention, FBI procedure, and the Amish community.

A well-written, comprehensive crime novel where Blood Rock Sheriff Serenity Adams is engaged as an FBI special agent because of her understanding of the Amish way of life. Reluctantly teaming up with a journalist named Mallory Miller, she uncovers links between the deaths of several families under suspicious circumstances.

Full of intrigue and unexpected finds, the story swept me along in a couple of days. I thoroughly enjoyed the mystery and sinister undertones throughout the book and applaud the author's ability to engage her audience in a concise, direct, and pacy manner.

I am grateful to have been given the opportunity to read this eARC by the author Karen Ann Hopkins and Book Sirens. I am leaving this honest review willingly.

[Gee · Rating 4 out of 5]

Sheriff Serenity Adams is on to a new chapter in her life - as an FBI agent, albeit not a full time one, but as an Amish specialist. It takes her away from home - again - but she knows it’s almost her calling to find justice for the victims. As usual it’s a well plotted story, bringing old and new people into her world, and disrupting her home life. It’s fast paced, intriguing and also leaves the reader (particularly this one) wanting more. I would have liked more about Daniel and what’s happening back at her main job, as Sheriff but that’s just a minor niggle. There’s also one slight error, that to a Brit would stand out - serial killer, Harold Shipman, wasn’t a General, he was a GP (General Practitioner) or just Doctor. That aside, a really good read.

I received an advance review copy for free, and I am leaving this review voluntarily.

[Anne G. Kasaba · Rating 5 out of 5]

Loved this book. The storyline is creative the book is well written. The characters are engaging. It was interesting to see Serenity out of her comfort zone, in a different Amish community without her usual team and support system. She is as driven as ever about solving mysteries and as torn between her family and bringing justice and righting wrongs as ever. This is a phenomenal series that I can’t recommend highly enough.

I received an arc of this book and voluntarily provided a review.

[Delphia Von Heeder · Rating 5 out of 5]

Sinister Summer is Book 21 in the Serenity Plan Secrets Series by Karen Ann Hopkins. Sheriff Serenity is expanding her law enforcerment and becoming a part time FBI Agent. I found this mystery to be interesting. The murders are taking place in the Amish community. The killer is a total psychopath and I found the ending to he unexpected. This is a very good mystery. I received an arc for free and am leaving my review voluntarily.

[Kathryn Read · Rating 4 out of 5]

Sinister Summer continues the long-running Serenity’s Plain Secrets series with its trademark blend of small-town intrigue and layered mystery.

In this latest episode Serenity's new professional responsibilities are in the foreground, whilst her personal life bubbles along almost under the surface.

I received an advance review copy for free, and I am leaving this review voluntarily.

The ending was pretty unsettling and extremely shocking

[Margaret Yelton · Rating 5 out of 5]

Sinister Summer by Karen Ann Hopkins is the 21st book in the Serenity's Plain Series, this was an amazing addition to the series. This was one of my favorite reads of the whole series. I would definitely recommend this book to everyone.

I received an ARC from BookSirens for free, and I am leaving my review voluntarily.

[Nancy · Rating 5 out of 5]

I received an advance review copy for free, and I am leaving this review voluntarily.

I thoroughly enjoy reading all of these Amish mysteries. I find myself getting totally immersed and unable to stop reading. Highly recommended.

[Susan · Rating 5 out of 5]

They just keep getting better. I love these books!!

[Barbra Reeder · Rating 5 out of 5]

Loved it!

She did it again, kept me glued to the pages till I was done. Now I'm sad I read it so fast.