1977. A family is murdered in cold blood. The case goes unsolved for decades and remains a mystery. Enter the present day, detective Lee Southward is sent on assignment to infiltrate an illegal underground fighting tournament and bring in the organizers. Lee battles his way to the top of the tournaments in attempts to get closer to the organizers. As Lee draws closer and begins to piece clues together he is brought back to the case closed decades ago. However there is a problem: The organizers are of the undead and crave human blood! Lee must fight his way through all the sex, drugs, and violence of the underground while trying to piece together evidence with the help of an undercover officer and find a way to stop the undead!

A cursed antique toy monkey from the original DeFeo home wrecks havoc and possesses a father after being gifted during an annual family reunion.