Homicide detective Catherine Palmer (Ellen Barkin) pursues a sexually deviant serial killer. The mysterious and seductive Vickie Kittrie (Peta Wilson) reveals that each victim belonged to an elite club of beautiful, prominent, and sexually experimental women. To catch the killer, Catherine must trust Vickie to guide her through this dangerous erotic underground in which no desire is forbidden and no one is who she seems. At the heart of the deadly mystery is psychotherapist Dominick Broussard (Julian Sands), who knows every uncontrollable impulse of his patients and harbors secrets of his own. Mercy is a highly-charged erotic thriller that seduces the audience into the most intimate relationship of all - between killer and victim.