Falling Darkness

S4 E4: Dr. Hobson finds herself caught up in a decades-old vendetta when one of her university friends is murdered, and another young student is killed in the house Hobson and her friends shared years ago. Obviously unable to act as the pathologist in the case, Hobson instead finds herself and her remaining friends—Dr. Ellen Jacoby and playboy Alec Giles (Rupert Graves, Sherlock)—suspects, and Lewis is forced to subject her to questioning.