The Sandin home, protected by an ostensibly high-quality security system sold far and wide by the family's father and head of household, becomes the target of a masked group of young holiday "Purgers" whose economically disadvantaged and severely wounded victim, referred to as homeless by the leader, escapes and is given refuge by the youngest child of the Sandin family. Frustrated by the interruption of their ritual sacrifice, the sadistic gang leader unmasks himself and threatens the entire family with murder if they don't surrender the man with the hour, or whenever reinforcements arrive with the equipment they need to bust through the barricades. After initially trying to capture the man and leave him to suffer his fate with the purgers, the family decides to help the man whose pain is no longer remote and can't be ignored, thus opening themselves up to accusations of unpatriotism. The purgers manage to break in and brutal fighting ensues with casualties on both sides. Losing their advantage, the family is about to be killed until they are "saved" by their neighbors, who blast away the remaining purgers to then announce that the Sandins' lives are their neighbors' to take. Facing execution by former friends, the stranger, who managed to escape most of the fighting, helps the Sandins by disarming the jealous neighbors. Faced with the choice of killing their neighbors, which in this world would be well within their rights, the family decides to hold them hostage until Purge night is over, further highlighting their unwilllingnessless to participate in the killing holiday.