A space shuttle mission investigating Halley's Comet brings back a malevolent race of space vampires who transform most of London's population into zombies. The only survivor of the expedition and British authorities attempt to capture a mysterious but beautiful alien woman who appears responsible.
When the dastardly Sheriff of Nottingham murders Robin's father, the legendary archer vows vengeance. To accomplish his mission, Robin joins forces with a band of exiled villagers (and comely Maid Marian), and together they battle to end the evil sheriff's reign of terror.
Mrs Warren, a London lodging-house keeper, comes to Holmes with a curious story of a reclusive and eccentric tenant. Mrs Warren's husband has been abducted and then quickly released again, perhaps a case of mistaken identity. Holmes decides the case is more important than it appears.