A connection to a 16th century murder seems to confirm that someone is killing witches in Whitechapel, but the investigation is impeded when a link to present-day espionage attracts the attention of the security services. Chandler is on the case, only for it to appear that there may be a malign influence at the very heart of the team. The station pulsates with unexplained phenomena, and even Miles starts to ask questions. Is anywhere truly safe, and who or what is behind the evil that seems to be surfacing all around?