 A few leads point to the docks by the Thames, and there, Holmes and Watson learn that similar kidnappings of foreigners have occurred.Further investigation leads them to an abandoned subterranean temple, where they discover a bloody and tortured corpse upon a sacrificial altar.They also find opium with morphine which leads Holmes to deduce that it is being used as a kind of soporific to subdue victims, so that they can be abducted and trafficked out of the country.