DI Lewis and DS Hathaway are called to investigate when Professor Ligiea Willard's body is found staked through the heart. A distraught Dr Laura Hobson informs the detectives that Ligiea was an old university friend of hers and that she never showed up to a pre-arranged social gathering with her and another friend, Dr Ellen Jacoby. The next morning, a group of Oxford students wake to find a mysterious message written on their fridge. When one, Rowena, decides to notify the police, the others suggest that they hold a seance to discover the culprit. A medium declares that a terrible deed had been commited in the room years before, but now all is at peace. When Rowena is found murdered the next day along with another mysterious message, Lewis and Hathaway delve deeper and learn that Laura and Ligiea had lived in the same house, along with Ellen Jacoby and two others. When Ellen is attacked and left in a coma, Lewis realises that the reason for the killings may lay in Laura's past.