Dead bodies are found on the streets of London with wounds that can only be explained as the work of ferocious creatures not native to the city. Sherlock Holmes is visited by his brother, Mycroft, who is only too aware that the bodies are the calling card of Dr Moreau, a vivisectionist who was working for the British Government, following in the footsteps of Charles Darwin, before his experiments attracted negative attention and the work was halted. Mycroft believes that Moreau's experiments continue and he charges his brother with tracking the rogue scientist down before matters escalate any further.