Butcher Benton goes to his death in the state prison, cursing those who double-crossed him following an armoured car hold-up. He vows to return and kill them and dies without revealing the location of the stolen money. Detective Chasen is determined to keep working on the case until the stolen loot is recovered.
Benton's body is taken to Professor Bradshaw and his assistant for experimentation, and they manage to restore him to life, making him practically indestructible in the process. He takes off after his enemies, getting rid of everybody who stands in his way.
Benton takes to the sewers to recover the hidden loot and the police are powerless to stop him.
Come on... it's got Lon Chaney in it, what do you expect? :)