 When a mysterious "angel of death" poisons a series of hospital victims with cyanide, Detectives Goren and Eames suspect a nurse who fits the typical profile - but when others fall dead outside the care facility, the investigators must widen their search. Even when the cops discover the source to be tainted, over-the-counter painkillers, the victims continue to pile up, and they can t gain any traction with their case until they find a motive -- or at least a source of the killer substance.