Dean and Sam decide to investigate the drowning of eighteen-year-old Sophie Carlton as she is the third drowning victim in the last year whose body hasn't been recovered from Lake Manitoc.

They pose as federal wildlife officers and speak to the local sheriff, Jake Devins, who tells them that they have found nothing in the lake despite running a sonar sweep, but that the lake will soon drain away because the local dam is leaking. While they are at the sheriff's office, they also meet Jake's daughter, Andrea Barr, and her son, Lucas.

When Sam and Dean research the lake further, they learn that not only have six other people disappeared in Lake Manitoc over the last 35 years, but also that Lucas witnessed his father's drowning earlier that year.

Sam and Dean decide to talk to Lucas and they find Andrea and Lucas at the park. Dean tells Lucas he knows what it's like to see something that most people wouldn't believe and draws the boy a picture of his family. Lucas remains silent but draws Dean a picture of a house. Andrea is stunned when Lucas gives Dean the drawing, as Lucas has been withdrawn and has not spoken at all since his father's death.

That same night, Will Carlton drowns in the kitchen sink when something drags his head below the surface of the water. Sam informs Dean of Will's death, and they conclude that whatever is in the lake knows the lake is being drained and that it is running out of time to get its revenge. They also assume that Sophie and Will's father, Bill Carlton, were somehow involved, as the thing in the lake has targeted his children and his godson, Lucas' father. They don't learn anything from Bill when they go to speak with him, but Dean notices that the drawing Lucas gave him earlier was of the Carltons' house.

The brothers visit Lucas again and Dean tells him about his own experience of losing his mother. Lucas provides Dean with a second drawing depicting a house next to a white church and a boy wearing a cap with a red bicycle. Sam and Dean find the church and the neighboring house, and they visit the woman who lives there. They discover that her son, Peter Sweeney, vanished 35 years ago with his red bicycle. Dean spots a photo of Peter with Bill Carlton, and the brothers start to think that Bill may have killed Peter and the thing in the lake was Peter's vengeful spirit. They go back to talk to Bill, but as they arrive they witness Bill making his way out to the middle of the lake in his boat. The boat flips over by an unseen force, and Bill vanishes under the water.

Lucas leads them to a spot near the lake where Sam and Dean dig until they discover Peter's bicycle. Jake appears and holds the brothers at gunpoint. He reveals that he and Bill buried the bike there after they accidentally drowned Peter and let his body sink in the lake.

“LUCAS!” The group calls out as they see him try to reach for something he dropped in the water but suddenly, Lucas is pulled into the lake by a ghostly hand.

Jake sees the corpse of Peter for a quick second.

“ANDREA! Stay on the dock!” Sam orders the woman.