Marnie Watson (Famke Jannsen) is being driven home in a police car after killing her abusive husband in self-defense - to be placed under house arrest. She is escorted home by Shanks (Bobby Cannavale) a police officer and former partner of her husband. After they get inside, another officer arrives to fit Marnie's ankle bracelet, telling her she cannot move more than from the detector in the hallway, and if the alarm sounds for more than three minutes, the police will be notified.