A wealthy family is held hostage for harboring the target of a murderous syndicate during the Purge, a 12-hour period in which any and all crime is legal.

Ben's high school sweetheart, Ava, returns to town after 20 years for her mom's funeral. Ava's between husbands and Ben's happily married and has a teenage son.

After watching their best friend get murdered, a group of teens struggle to expose a local hero as the vicious killer and keep from becoming his next victims.