Jim Napier is a retired naval officer who plans a fishing trip to Platoon Lake with his grandson Reece, an amateur paranormal investigator. After encountering strange events on the way there, Reece begins to research the area and finds that hundreds have gone missing in and around the lake, with the locals attributing the missing cases to the Q'thahkal. Jim is skeptical about the urban legend and decides to continue on with the trip, despite Reece's objections. This decision will soon prove to be a deadly one, as the beast of ancient times reveals itself.