The Chinese Secret Service sends an undercover agent to investigate reports of an island ruled by a Chinese criminal named The Cobra who holds the residents in virtual slavery while running his illegal narcotics and white-slavery empire.
One dark and stormy night, an escaped convict, an embezzler, a runaway daughter, her intended and her father, and a gangster take refuge in a remote inn called "The Black Raven" after the nickname of a second gangster who owns it; and murder ensues.
In Victorian era London, the inhabitants of a family home with rented rooms upstairs fear the new lodger is Jack the Ripper.