One Halloween, Ligiea Willard, stem-cell researcher and ex-roommate of Laura Hobson, is killed on her way to a reunion with Laura and another old friend named Ellen Jacoby. Her work attracted protests, and she was about to go public on shady practices at her institute. Psychic Ursula Van Tressell senses the killing and exorcises a house where the three women once lived at its owners' request. The next day, a resident is found slain, and a message on the fridge urges to find Mary Gwilliam, who was also murdered after trying to phone Laura. Mary was a nurse at a mental hospital where another of Laura's roommates--and boyfriend--died. After an unsuccessful attempt to kill Ellen, Lewis, her boyfriend, realizes that Laura has not been honest with him.