Harley Granger has a gift for seeing things that others miss. He wasn't much of a novelist, but his work as a true crime author and podcaster has earned him fame and wealth—and some serious criticism for his various unethical practices. Still, visiting Little Valley to be closer to his dying father has caused him to look into a case that many people think is closed—and some want reopened.

Years after a breakdown and a diagnosis of dissociative identity disorder derailed her historical preservationist career, Kenetria Nash and her alters have been given a second chance they can’t refuse: a position as resident caretaker of a historic home. Having been dormant for years, Ken has no idea what led them to this isolated Hudson River island, but she’s determined not to ruin their opportunity.

When Caz steps onboard the exclusive cruise liner RMS Atlantica, it’s the start of a vacation of a lifetime with her new love, Pete. On their first night they explore the ship, eat, dance, make friends, but when Caz wakes the next morning, Pete is missing. And when she walks out into the corridor, all the cabin doors are open. To her horror, she soon realizes that the ship is completely empty. No passengers, no crew, nobody but her. The Atlantica is steaming into the mid-Atlantic and Caz is the only person on board. But that’s just the beginning.

It was supposed to be just one night in the cabin: one night for Lottie and her brand new stepsister, Jade, to try to get along. When a solar flare causes a massive blackout—no power or cell signal—Lottie knows they've got a long night ahead of them. Then, in the dark, someone else shows up at the cabin—a stranger named Alex, claiming to be lost and needing shelter from the coming snowstorm. But later that night, Lottie spies him in the driveway talking to two mysterious men in a pickup truck, and she's sure he's lying about why he's here.

10:00 a.m. The principal of Opportunity, Alabama's high school finishes her speech, welcoming the entire student body to a new semester and encouraging them to excel and achieve. 10:02 a.m. The students get up to leave the auditorium for their next class. 10:03. The auditorium doors won't open. 10:05. Someone starts shooting. Told over the span of 54 harrowing minutes from four different perspectives, terror reigns as one student's calculated revenge turns into the ultimate game of survival.