A determined but somewhat absent-minded skiptracer named Maggie McKeown is dispatched to find the missing teenagers near Lost River Lake. She hires surly backwoods drunkard Paul Grogan to serve as her guide. They come upon the abandoned compound, which functioned as a fish hatchery before being militarized. They discover bizarre specimens in jars and indications of an occupant. Maggie locates the drainage switch for the outside pool and decides to empty it to search the bottom, but the moment she activates it a haggard man appears and tries to stop her until he is subdued by Grogan. The two find a skeleton in the filtration trap of the empty pool, and learn it was filled with salt water. The man awakens and steals their jeep, but crashes it due to his disorientation, and is taken to Grogan's home where they spend the night. They take Grogan's raft down the river, where the man wakes up and tells them that the pool in the facility was filled with a school of lethal piranha fish, and that Maggie has released them into the river. They are skeptical until they hear a dog barking and they come across the corpse of Grogan's friend Jack, who has bled to death from an attack on a fishing dock.