It is June 21, the longest day of the year, and the life of new mother Camilla is about to change forever. After months of maternity leave, she will drop off her infant daughter at daycare for the first time and return to her job as a literary agent. Finally. But when she wakes, her husband Luke isn’t there, and in his place is a cryptic note. Then it starts. Breaking news: A hostage situation is developing in London. The police tell her Luke is involved—but he isn't a hostage. Her husband—doting father, eternal optimist—is the gunman.

Can you stop a murder after it’s already happened? It is midnight on the morning of Halloween, and Jen anxiously waits up for her 18-year-old son, Todd, to return home. But worries about his broken curfew transform into something much more dangerous when Todd finally emerges from the darkness. As Jen watches through the window, she sees her funny, seemingly happy teenage son stab a total stranger. She doesn’t know who the victim is, or why Todd has committed such a devastating act of violence. All she knows is that her life, and Todd’s, have been shattered. After her son is taken into custody, Jen falls asleep in despair. But when she wakes up… it is yesterday. The murder has not happened yet—and there may be a chance to stop it. Each morning, when Jen wakes, she is further back in the past, first weeks, then years, before the murder. And Jen realizes that somewhere in the past lies the trigger for Todd’s terrible crime…and it is her mission to find it, and prevent it from taking place.

In this tightly wound, enthralling story reminiscent of Agatha Christie’s works, Lo Blacklock, a journalist who writes for a travel magazine, has just been given the assignment of a lifetime: a week on a luxury cruise with only a handful of cabins. The sky is clear, the waters calm, and the veneered, select guests jovial as the exclusive cruise ship, the Aurora, begins her voyage in the picturesque North Sea. At first, Lo’s stay is nothing but pleasant: the cabins are plush, the dinner parties are sparkling, and the guests are elegant. But as the week wears on, frigid winds whip the deck, gray skies fall, and Lo witnesses what she can only describe as a dark and terrifying nightmare: a woman being thrown overboard. The problem? All passengers remain accounted for—and so, the ship sails on as if nothing has happened, despite Lo’s desperate attempts to convey that something (or someone) has gone terribly, terribly wrong…