Juan and his wife Adela are Mexicans crossing the border to Texas. They make it safely and their guide says if they ever need help, "Follow the roses." Meanwhile, the New Founding Fathers of America (NFFA) have returned to power and reinstated the Purge.
Ten months later, Adela works in a restaurant under the manager Darius. Juan, his Mexican friend T.T., and Kirk work as ranch hands on a farm owned by the elderly Caleb Tucker, his son Dylan, Dylan's pregnant wife Cassie, and Dylan's sister Harper. Dylan resents Juan for being Mexican and more talented than him, like when Juan easily calms a horse that injured Dylan.
The Purge is coming up, so Caleb pays the ranch hands extra money and urges them to get to safety. The Tuckers hole up in their home while Juan, Adela, and T.T. go to a shelter. As the Purge starts and people start rioting and looting, Adela joins the guards on the roof and sees armored trucks rounding up and slaughtering minorities. She grabs a gun and tries to shoot them, but a guard persuades her not to so they don't escalate the violence.
The next morning, the Purge is over. Adela goes to work and finds a goat in a cage outside. She tries to free it, but gets caught in a booby trap and is attacked by masked men who declare this is the Forever Purge. Darius rescues her and they kill the men together, only to get arrested by an arriving officer. They are put in a police van with a woman and a murderous Neo-Nazi. The van gets attacked by rioters and flips over. The impact kills the woman and the Neo-Nazi breaks his bonds and attacks Adela. Darius breaks his bonds and manages to kill him.
The Tucker family gets captured by Kirk and his gang of Ever After Purgers. Kirk wants revenge on the Tuckers for being rich and keeping poor people like him down. Caleb calls him a hypocrite because the Purge was created by rich people, but gets shot in the head. Juan and T.T. arrive and kill Kirk and his gang. They get in Dylan's truck and manage to find Adela and Darius while dodging rioters. Darius decides to stay and find his family, while the rest drive out of the city. They stop at a gas station and learn from a radio that the Ever After Purgers are attacking everywhere in the US, mostly targeting minorities and the government. Canada and Mexico have opened their borders for six hours to allow US citizens in for their safety. The group drives to the Mexican border. They get attacked by Ever After Purgers on motorcycles, but Harper pulls out an Ever After Purge flag she acquired to trick them into thinking they are on the same side. During the drive, Dylan makes peace with Juan.
They arrive in El Paso and find the Ever After Purgers at war with the military. The road is blocked, forcing them to travel on foot. A tank shell explosion separates Adela and Cassie from the others. Adela notices rose murals forming a trail and decides to follow them. After seeing Adela expertly handle her gun and easily kill attackers, Cassie asks how she is so skilled, and she answers that she and Juan used to fight the drug cartels in Mexico together. Juan's group also follows the roses, but get captured by Ever After Purgers led by Elijah Hardin and his wife "Mother". Since Dylan and Harper are white, they offer to spare and let them join if they kill their Mexican comrades, but they refuse. Mother kills T.T., but they are attacked by the military, allowing Juan's group to fight their way out. Juan kills Mother before escaping, causing Elijah to swear vengeance.
The rose murals lead to a shelter where they are reunited. The news reports that the Ever After Purgers have bombed a military base, forcing the military to withdraw and the borders to close immediately. The refugees are driven to a Native American reservation on the border, but are pursued by Elijah and his gang. The refugees still have to cross a mountain to reach Mexico. Harper helps lead Cassie and the refugees across while Dylan, Juan, Adela, and a few volunteers stay to fend off the Ever After Purgers. They run low on bullets, forcing them to use improvised weapons, but they manage to kill them all, including Elijah. The trio cross the mountain into Mexico and find Cassie and Harper in a hospital, where Cassie has given birth to a girl. Dylan holds his daughter and thanks Juan in Spanish for saving him and his family.
The news reports that the Ever After Purgers have destroyed the NFFA and America is in total chaos, but several citizens are fighting back.
