Leslie Calloway is a twenty-eight-year-old volunteer at a 1-800 line, designed as a call center for children whose parents are out of the house. One snowy New England night, she receives a panicked phone call from a young boy named Justin. He says, "There's a man in my house," and Leslie is the only person who can save him.
Armed with only a handheld receiver, Leslie must use experience, intuition, and love to talk her young caller through his ordeal. The hushed conversations lead to a shared intimacy which forces Leslie to take a closer look at the boy's domestic situation, which makes her peer unwillingly into the darkened corners of her own life and state of mind.
As the intruders get closer to Justin and become all the more threatening, Leslie realizes that despite the frigid weather, she must get the boy out of his house and to safety. Danger soon takes an unexpected personal turn. By then, it's too late to turn back: Leslie is part of Justin's life, and she will stop at nothing to keep an innocent child safe from monsters of the night.