The group struggles with the traumatic turn of events as they realize they are being targeted by Mick, and make their way toward a hill in search of water and civilization.
Police Lt. Kinderman (George C. Scott) notices similarities between his current murder investigation and the methods used by the Gemini killer (Brad Dourif) who was executed 15 years before. He soon discovers a hospitalized mental patient (Jason Miller) claiming to be the dead serial killer, but who looks uncannily like a priest Kinderman knew who died during an exorcism. As more bodies are found, Kinderman looks for connections between the two supposedly dead men.
A scientist, a sheriff, an exterminator and an island mayor's daughter go on the hunt for mutant meat-eating cockroaches that are terrorizing a peaceful New England fishing village.