Falling Darkness

S4 E4: It's Halloween and Lewis and Hathaway are called out to the body of Professor Ligiea Willard, found with a stake through her heart. A traumatised Doctor Hobson arrives on the scene and reveals that Ligiea was an old university pal and they'd been due to meet for a drink along with another friend, Dr Ellen Jacoby, that very evening. Lewis and Hathaway then receive a visit from Ursula Van Tessel, a medium who claims to have foreseen Ligiea's death.