Libby and her son, Ethan, are on a much-needed vacation. But in a moment of inattention, Ethan wanders into an elevator before Libby can reach him. When the elevator stops and the doors open, Ethan is gone. Hotel security scours the building and finds no trace of him, but when CCTV footage is found of an adult finding the child wandering alone and leading him away by the hand, the police are called in. The search intensifies, a lost child case turning into a possible abduction. Hours later, a child is seen with a woman stepping through an emergency exit. Libby and the police track the woman down and corner her, but she refuses to release Ethan. Asked who she is, the woman replies: "I'm his mother."

It begins with a woman fleeing through Arizona with her kids in tow, trying to escape an abusive marriage. When she's pulled over by an unsettling local sheriff, things soon go awry and she is taken into custody. But when she gets to the station, her kids are gone. And then the cops start saying they never saw any kids with her; if they're gone, she must have done something with them. Meanwhile, halfway across the country, a man hears the frenzied news reports about the missing kids, which are eerily similar to events in his own past. As the clock ticks down on the search for the lost children, he, too, is drawn into the desperate fight for their return.