This post-apocalyptic future story is based on the 8th century Saxon epic poem about the knight who battled a monster in a medieval castle. In this story, Beowulf is a wanderer who learns about a man-eating creature called Grendel which comes in the night to devour warriors trapped at the Outpost. The Outpost is ruled by Hrothgar. He has a daughter, whose husband may have been murdered by the Outpost's master of arms.

On her first trip to Paris, a young woman hits a party in the Catacombs, the 200-mile labyrinth of limestone tunnels under the city that's lined with the remains of 7 million people. Separated from her friends, she becomes convinced that someone or something is chasing her.

Picking up immediately where Anaconda 3 left off, herpetologist Amanda Hayes finally learns her employer Murdoch's true colors when he hires a doctor to harvest a fresh supply of blood orchids to experiment with the regenerative nectar on a baby snake in order to seek treatment for his own terminal illness. Amanda is forced to secretly bring together another team of scientists whom face off against a heavily armed squad of Murdoch's men to steal the coveted orchids before the killer Anaconda hunts both parties down.