In 1893 Yorkshire another dead man is found, his body red from head to toe. The locals are calling it the crimson horror. Madame Vastra, Strax and her maid Jenny soon travel to the North after they find that the latest victim's last sight was of the Doctor. Vastra thinks she seen this red covering before, a very long time ago. Meanwhile Winifred Gillyflower, a prize-winning chemist and chemical engineer, has established a new industrial community known as Sweetville. Jenny goes to get a job there but sneaks off only to find that Sweetville's factories are fake - there's nothing in the large buildings but very large loudspeakers making factory noises. She does find and free the Doctor and together with Clara fight off the creature that is behind it all.
—garykmcd