4In the attic of a deserted tenement, the body of a criminal is found hanging with his face horribly mutilated. Investigating officers Detective Inspector Anderson and Detective Sergeant Costello believe he was a suspect in a decade-old case: the rape and attempted murder of a young student. There are other similar cases on file. But the dead man didn't act alone. He had an accomplice in his crimes.

When another young woman is brutally attacked, Anderson and Costello suspect the accomplice has developed a taste for killing. To satisfy his lust he will kill again and again unless Anderson and Costello can stop him.