Police is investigating a series of killings of high-society people, both men and women, apparently unrelated.
Somehow, it's revealed that whomever is killing them, is targeting members of a BDSM/cuckolding club. But only the masters, the subs are apparently being left alone.
Although interrogated, the club members don't tell the police that a female sub accidentally died during one of their parties, and that the sub's husband wasn't aware of his wife's activities. Apparently he had killed himself when he discovered her betrayal, but now it seems he's still alive and going for revenge.