Whitechapel - Season 4 Episode 2

Buchan theorizes that the killer believes they are a modern Witchfinder General and that the markings on both Dorothy's house and the scene of Alexander's murder are to warn off evil spirits, though homeless Lee Bysack claims they are to show houses friendly to vagrants. Another woman is killed and it seems that each victim gave the murderer the name of an associate, who was then slain. Dr. Llewellyn tells Chandler that Dorothy's killer lost a finger through gangrene and Buchan explains that the gangrene was probably the result of ergot poisoning, which causes madness and paranoia. This leads to a disused bakery and a killer who believes they were cursed by witchcraft as the police manage to save the last victim.