Tom Baker
The Talons Of Weng-Chiang

The Doctor and Leela visit Earth at the end of the nineteenth century. A series of murders have been committed by a Chinese Tong of the Black Scorpion led by Weng-Chiang.

The Doctor makes friends with a police pathologist, Professor George Litefoot. A hair sample taken from one of the dead bodies appears to have come from a giant rat. Investigations by the Doctor in the sewer show there are indeed giant rats.

The trail leads to the Palace Theatre where the Doctor finds Li H'Sen Chang, who has been procuring young women for his master, Weng-Chiang. Weng-Chiang is in fact Magnus Greel, a war criminal from the 51st century. The journey back through time had weakened his molecular structure and he needed the life-force of the young women to stay alive.

Greel had returned to London to obtain his time cabinet which was in the possession of Litefoot, using the Peking Homunculus to infiltrate Litefoot's house and retrieve the Time Cabinet. The Doctor manages to trap Greel, who falls back into the life-force extraction machine and disintegrates.