The sister of a famous, but as yet uncaught, criminal named "The Hexer" is murdered. Inspector Higgins of Scotland Yard believes that "The Hexer" will surface to take his revenge on his sister's killers, and plans to set a trap to finally capture him. However, soon bodies start piling up, and it looks as if "The Hexer" may get away yet again.
Arthur Milton aka Der Hexer (The Magician/Ringer) must return to London after his calling card was left at the scene of a murder he did not commit.
When another dead elderly gentleman is fished out of the Thames, Inspector David Perkins is convinced that the gorilla gang is active again. On a doll found with the body, characters of an African language are discovered. Together with Sergeant Pepper and language specialist Susan MacPherson, the search for the head of the gang begins.
