When a prominent politician and a beautiful young woman vanish inside a London subway station, Scotland Yard’s Inspector Calhoun (Donald Pleasence) investigates and makes a horrifying discovery. Not only did a group of 19th century tunnel workers survive a cave-in, but they lived for years in a secret underground enclave by consuming the flesh of their own dead. Now the lone descendant of this grisly tribe has surfaced, prowling the streets for fresh victims… and a new mate!