The sudden collapse of the Thames embankment opens a passage into the mysterious underground world of London. Aristocratic inventor Langdon St. Ives and his friends decide to explore unknown spaces, not knowing that they are opposed by a cold-blooded genius of evil, in front of whom the demonic Doctor Narbondo will seem like a mere child! On the side of the psychopathic murderer is the entire underworld of the British capital, the deadly inventions of the vivisector Peavy, and even vampire mushrooms. Murders and kidnappings of innocent people follow one after another... Will St. Ives be able to avoid the sad fate prepared for him and restore peace and tranquility on the streets of London?..