Newly single mom Beth has one constant, gnawing worry: that her dreamy eight-year-old daughter, Carmel, who has a tendency to wander off, will one day go missing. And then one day, it happens: On a Saturday morning thick with fog, Beth takes Carmel to a local outdoor festival, they get separated in the crowd, and Carmel is gone. Shattered, Beth sets herself on the grim and lonely mission to find her daughter, keeping on relentlessly even as the authorities tell her that Carmel may be gone for good.