Adam Crowley, a once-respected scientist, now turned to black magic, has released a demonic contagion onto the streets of London in 1834. Based on the long-lost work of the Brotherhood of Hecate, it mutates its victim's bodies into grotesque nightmare creatures, and changes their minds into those of murderous brutes. When Dr. Jean F. began investigating, he was murdered. Now, as either his friend Ignatius Blackward, a priest and expert on the occult, or his daughter Nadia, a biologist and gymnast, fight against the creatures that roam the streets of London, the revived Brotherhood of Hecate, and the man behind it all, Adam Crowley.