In a dark future, crime and prison overcrowding is so rampant, the U.S. government allows a 12-hour period during which all crime is permissible. One suburban family risks everything when they take in someone wanted by a bloodthirsty mob.
With the annual Purge providing 12 hours of sanctioned unlawfulness, a grieving father's quest for revenge on his son's killers takes a turn when he comes across four helpless strangers who were stranded on the streets during a night where being out means being dead.
Two years after his son's murder, Leo Barnes, who now works as a head of security for Senator Charlie Roan, finds himself obliged to ensure the Senator survives the mayhem that is the purge night. She is in danger because of her vow to eliminate the Purge.
When a new political party takes over the government, they conduct an experiment aiming to decrease the crime rate. For twelve hours, there will be no laws governing the streets of Staten Island. But when the surge of violence spills out of the city, it gives the first spark to a nation-wide event.
As Adela and Juan, a Mexican couple, escape the clutches of a drug ring, they end up in Texas, where they come up against a group of desperados, who are determined to make the annual Purge day last forever.