Greta Helsing, a doctor of impeccable reputation, inherited her father's practice. For the past five years, she has been providing Harley Street first aid to patients who, for most of us, do not exist: vampires, werewolves, mummies, banshees, ghouls, caveman rheumatics. Treating others is a family matter. The monsters are not bloodthirsty and are considered fiction, until one day religious fanatics, one in one like Greta's patients, emerge from gloomy tunnels, attacking the world of the living and "not the dead." Now London is a very frightened city.