Plot summary

After spending two years living with his Aunt Sarah in Florida, troubled teenager Neal Hausman returns home with his father Terry. Neal has been gone since setting fire to the family home in an incident that claimed his mother's life. Terry has since remarried a woman named Angela and they are attempting to normalize the family. Terry is frustrated with Neal's emotional distance and lack of communication.Neal finds a "Welcome Home" party waiting for him at the house. Neighbor Mr. Evans invites Neal to his house for a sleepover with his sons Richard and Robert. Neal also reconnects with Mr. Evans' daughter Cara, with whom Neal had a relationship in the past. Neal goes upstairs to his old bedroom and reunites with his younger brother Paulie. Terry discovers that Paulie has been going through boxes of Neal's things from before the fire. Furious, Terry scolds his two sons and abruptly ends the party.The two brothers ride their bikes to Melanie's Diner. Paulie reveals that he knows his brother is not crazy because he sees the same creature that haunted Neal before his breakdown. Meanwhile, back at the house, the creature frightens Angie while she does laundry, although she never sees it. After a brief encounter with Cara and two bullies, the boys return home for dinner with their father and stepmother.Paulie falls asleep at school and a nightmare causes him to wake screaming. Terry lectures his sons about their poor behavior and their seemingly irrational fear of sleeping. The boys are sent to bed and their father locks the door. Paulie shows his older brother how he runs and jumps into bed to avoid the creature lurking underneath. Neal sleeps on the dresser to avoid the floor. In the night, a mist envelops the room as everything begins to shake. A vision of their deformed father chokes Paulie while Neal tries fighting him off. The real Terry enters the bedroom and finds Neal with his hand around Paulie's throat. Thinking that Neal was responsible, Angie treats the wound on Paulie's neck. Terry thinks Paulie did it to himself. Terry takes the light bulb out of the bedroom to force his sons to sleep in the dark. Both boys end up sleeping on the dresser.Paulie shows Neal the urn of their mother's ashes that he keeps hidden in the garage. Neal admits that he begged their mother to stay in the house the night of the fire so that she could see what was under the bed. Neal believes she died because she believed him. The brothers look for things in the garage that they can use as weapons. Angie stops Neal from using the chainsaw. The boys then create makeshift tools including a pole with three flashlights attached. Neal theorizes that the monster may feed on dead skin cells left in the bed.That night, the mist returns along with the creature, who emerges out of Neal's old bed. The boys escape and the next day they are sent to the Evans house for a sleepover. Back at the Hausman home, a robed shadow stalks Angie. Neal and Paulie tell their story to Richard and Robert. As they do, mist enters the room. The creature appears and tears off Richard's head. Neal tells Cara to hide in the light in her room. Neal and Paulie jump out the window and run home. The creature follows them and kills Terry. The monster then takes Paulie under the bed.Neal prepares to rescue his brother by going under the bed. He ties a rope around himself with Angie holding on at the other end. Neal enters the monster's world and rescues his brother. The creature follows the boys back to reality and a fight ensues in the garage. When the urn is knocked over, Neal sees that his mother's ashes affect the creature. Neal talks a handful of her remains and destroys the monster with them. Reunited with Cara as well, the two boys then embrace their stepmother.