In 2025, two years after choosing not to kill Warren Grass, the man who killed his son in a drunk-driving accident, police sergeant Leo Barnes (Frank Grillo) becomes head of security for U.S. Senator Charlene Roan (Elizabeth Mitchell), the front runner in the next U.S. presidential election. Due to her vow to eliminate The Purge after losing her family to sadistic murderers on Purge-night 15 years earlier, Barnes continues to campaign against The Purge after witnessing the deaths during his night on the streets two years ago. The government secretly opposes Roan's campaign, and plots against her to keep her from destroying The Purge. On the night of what could be "the final Purge," a betrayal from within the government at the hands of the New Founding Fathers of America forces Barnes and Senator Roan out onto the street, where they must fight to survive the night, and come across a group of anti-Purge rebels that support Senator Roan's campaign.