James Murphy is a rugged cryptozoologist, who thirty years earlier, during a trip to Loch Ness, Scotland, had a fatal encounter with the fabled "Nessie" creature that killed his father, research assistants, and left James with a deep facial scar. Thirty years later, James is hunting for Nessie, when his search leads him to the sleepy town of Pike Island, Ashburn, on Lake Superior. He encounters Josh Riley, owner of a bait shop. Josh's ex-girlfriend, Zoe, is going camping along with Brody and two others on a small deserted island on the lake.
Josh's uncle, Sean, attempts to prove Nessie's existence but is eaten instead. James hires Josh as a guide while his mother, Sheriff Karen Riley, eventually finds Sean's remains. She begins to suspect that an underwater predator is on the loose. The creature attacks and kills her deputy's sister when she was out grocery shopping. When one of the campers disappears (after being eaten by the creature), the others are unable to escape and one is killed while Brody is injured.
Hearing about James, Karen warns him to stay away from Josh, but the pair still work together. They find a corpse and James takes the head before Karen's deputy, Neil Chapman, arrives. James reveals that Sean has contacted him prior about Nessie and, seeing the corpse, believes there might be a nest somewhere. Before the two set off, James is arrested, leaving Josh to go alone.
James manages to convince Karen that a 40-foot Plesiosaurus is behind the killings, after they send a skin sample to the Zoological Institute on the mainland that matches no known species of reptile. Josh arrives on the island and encounters packs of baby Plesiosaurus. He is rescued by Zoe and Brody and he leaves them at a magnetite mine for safety, not knowing it is the nest. Brody is killed by a pack of baby Plesiosaurus. Sheriff Riley, Murphy and Deputy Neil Chapman spot Josh's flare and track the creature and her offspring to the magnetite mine on the island.
Sheriff Riley and Josh manage to kill some of the offspring, Neil dies after running out of ammunition and being attacked by the babies. Josh lures Nessie away from Zoe and traps her in a container filled with magnetite. James stabs the creature with a cyanide-filled syringe, then helps Josh by getting him out of harm's way and throws his cigarette lighter into the container, igniting the explosive magnetite and destroying the creature and her remaining offspring. Josh and Zoe are reunited and Sheriff Riley asks if James will now start "chasing Sasquatch", to which he replies that he will instead probably find a nice small town to call home. Josh asks if he means Ashburn, to which he laughingly replies "yeah."
Brian Krause as James Murphy Niall Matter as Josh Riley Don S. Davis as Neil Chapman Donnelly Rhodes as Uncle Sean Carrie Genzel as Sheriff Karen Riley Amber Borycki as Zoe Neil Denis as Chad Sebastian Gacki as Brody Paul McGillion as Michael Murphy Serinda Swan as Caroleena Sam Laird as Young James Murphy David Lewis as Scientist #1 Alan Longair as Thomas Chapman Bart Anderson as Scientist #2 Suzanne Ristic as Marge Rob Morton as Bill Maxwell R. Nelson Brown as Fisherman
It aired on 5 January 2008 in the USA at Sci Fi Channel and was released on 9 July 2008 in Canada over DVD.