Beast (S04E19)

Lisa Ross (Elizabeth Hobgood) is beautiful, and married to a successful (but suspicious) dentist, Gregory (Bronson Pinchot). She is out with her friends and wins a sweatshirt in a bar quiz contest, but her husband suspects a man's cologne on it. The next evening, Lisa, her husband, and parents are supposed to go on a dinner cruise, but she gets violently ill and is taken to the hospital. Her face then gets horrible acne-like cysts, and it's dioxin poisoning. Initially, Detectives Goren (Vincent D'Onofrio) and Eames (Kathryn Erbe) think she may have picked up the dioxin at work, since she's in a basement and there are rusty bolts and the work conditions show traces of dioxin. But not nearly enough to give her the levels in her body, which ultimately kill her. (iTunes)