In the near-future America of The Purge, one night a year is reserved for violent crime: For twelve hours, the state sanctions, and even encourages, otherwise illegal behavior, including murder, with no criminal consequences. The idea is that the rest of the year there would be less crime, though one of the outcomes is that the Purge results in more crime against the lower classes, who can't afford to protect themselves. One family that can protect itself -- theoretically -- is headed by Lena Headey and Ethan Hawke, who has gotten rich from selling security systems to his resentful high-class neighbors. Their plan? Lock themselves indoors and wait it out while Purge participants rape, maim, and murder with glee. Of course, this being a movie, things never go according to plan -- not when you've got an underage daughter with an overage boyfriend, a son who empathizes with the downtrodden, and neighbors who exclude you from their Purge plans. Headey, who also plays the formidable Queen Regent on Game of Thrones and knows a thing or two about bloodlust, chatted with Vulture about purging violent emotions, a mother's love, and why her son thinks she's out fighting ninjas.