A backpacking trip gone awry tests the relationship of two best friends. Emily and Kristen, now almost 30, have been close since college, and as neither are close with their families, they're more like sisters than friends. Now it's time for their yearly trip to somewhere adventurous and off the beaten path, trips that have become even more important since Kristen moved to Australia for work a few years ago. Last year's trip was a disaster, though, ending when Kristen killed a man who'd been sexually assaulting Emily; now, on the last night of their trip to Chile, Emily finds Kristen standing over the body of the cute guy she'd brought back to their room, saying he'd been rough with her. Taken aback by the similarities to what had happened the year before, Emily helps her friend cover it up and heads back to Wisconsin, unsure how to deal with her newly reignited trauma. Just when she thinks she's ready to move on with her new boyfriend and therapist, Kristen appears on her doorstep as if nothing has happened. Bartz's latest thriller is full of twists and turns as Emily discovers new things about the friend she thought she knew so well. The dread creeps up slowly on both Emily and the reader as more and more comes to light and the truth slowly reveals itself. Up to the unexpected climax and beyond, Bartz's writing will keep readers on their toes, questioning everything and looking for hidden meanings in every communication between Emily and Kristen. While the last 10 pages or so may not quite live up to those that precede it, the overall plot is exhilarating. A slow-burn thriller that gradually suffocates both the protagonist and the reader--in a good way. Copyright (c) Kirkus Reviews, used with permission.

Backpacking through the Chilean mountains with best friend Kristen, Emily is shocked to learn that Kristen has killed a fellow backpacker, claiming self-defense. Another backpacker died on their last outing, and as Kristen becomes abruptly clingy Emily starts wondering what's happening. From the author of the multi-best-booked The Lost Night.

Milwaukee resident Emily Donovan, the narrator of this riveting psychological thriller from Bartz (The Herd), and her best friend, Kristen Czarnecki, who left Milwaukee 18 months earlier for a job in Australia, reunite in Chile for their annual vacation. The trip turns deadly when Kristen kills a backpacker in self-defense. A similar fatal encounter occurred during an earlier trip to Cambodia, only then Kristen killed to defend Emily. Emily decides she needs to distance herself from Kristen, but the more she tries to do so, the more Kristen tries to stay connected. Kristen moves back to Milwaukee, where she soon starts popping up in places she doesn't belong--such as Emily's yoga studio and therapist's office--constantly reminding Emily of the secrets they share and how they need each other. Bartz does a good job dramatizing the increasingly creepy relationship between the two women as the twisty plot builds to a slightly confusing conclusion. Suspense fans will look forward to seeing more from this talented author. Agent: Alexandra Machinist, ICM Partners. (July)

On a vacation trip to Cambodia, Emily and her friend Kristen meet a friendly, attractive man who accompanies Emily back to her room. When the man begins to act in a threatening manner, Emily asks him to leave. Violence ensues, and Kristen comes to her friend's defense. The man dies, and they dispose of his body. A year later, still trying to come to terms with what happened in Cambodia, Emily is on another trip with Kristen, this time in Chile. And, as unlikely as it might seem, the same thing happens again. Well--not quite the same thing. This time, it is Kristen who is attacked, and Emily is not present when her friend kills the man. Back home in the U.S., Emily is haunted by what Kristen has done (twice), and she must confront the most frightening question of whether her friend has a darkness within her that has remained hidden for years. Bartz takes a seriously (and deliberately) implausible premise and develops it in such an intelligent, methodical way that we have no trouble accepting the story. Emily and Kristen are two very interesting characters--they'd be right at home in a Hitchcock psychological thriller. A terrific novel, blending the Hitchcockian elements with a touch of Patricia Highsmith.