In this indirect sequel to the original Purge film, the story unfolds in Los Angeles on March 21, 2023, just two and a half hours before the chilling start of the Annual Purge, a night where all crime is legalized for 12 hours. As the clock ticks down, the anxious employees of a diner wait for their boss to release them. Among them is Eva (Carmen Ejogo), who later heads home to her father, Rico (John Beasley), and her teenage daughter, Cali (Zoë Soul). Meanwhile, Cali is engrossed in a video featuring Carmelo Jones (played by Michael K. Williams), a charismatic figure rallying against the New Founding Fathers and their oppressive actions towards the impoverished. Rico, deeply disdainful of the Purge, insists they refrain from discussing it that evening.
As tensions rise, Leo (Frank Grillo) is preparing himself for the chaos about to ensue. When Janice (Chad Morgan) knocks on his door, she stumbles upon his harrowing plans displayed through newspaper clippings. Despite her warnings, Leo feels compelled to follow through with his intentions.
Elsewhere, a couple, Shane (Zach Gilford) and Liz (Kiele Sanchez), navigate rising tensions between them as they drive through the city. After a brief stop, they are accosted by punks adorned in face paint, escalating the sense of imminent danger. Just as they get back on the road, their car inexplicably breaks down, and they realize malicious hands have sabotaged their vehicle.
As the Purge sirens wail to announce the beginning of the night, Eva prepares dinner with Cali, while Shane and Liz hide from the growing threat of Purgers. Leo ventures into the fray in his armored vehicle, witnessing horrific violence around him. Amidst the bedlam, Cali discovers a note from Rico revealing his plans to sacrifice himself for money, leading to an emotional confrontation between her and Eva.
When the lecherous neighbor, Diego (Noel Gugliemi), bursts in with malicious intent, he meets his end at the hands of armed men who then take the women captive. Witnessing this from the street, Leo decides to intervene, risking himself to save Eva and Cali, who are now joined by Shane and Liz. Their escape comes at a price as they find themselves on the run from Big Daddy (Jack Conley) and other ruthless Purgers.
As they traverse the urban landscape, they manage to find temporary refuge at the home of Tanya (Justina Machado). However, tensions rise again when a shocking betrayal leads to deadly chaos. When confronted with imminent danger, Leo devises a plan to ensure their survival at the hands of the wealthy audience that seeks entertainment in their demise.
With devastating consequences, Shane falls victim to the relentless Purgers, and Liz chooses vengeance over escape. As the night wears on, Leo faces his own haunting past as he targets Warren Grass (Brandon Keener) — a man responsible for a tragedy that struck Leo's family. At the brink of his revenge, Leo finds himself caught in a deadly showdown with Big Daddy, ultimately leading to an explosive conclusion as the Purge sirens signal the night's end.
In the aftermath, the survivors reflect on the violence they narrowly escaped while rushing Leo to safety, encapsulating a night marked by chaos and harrowing choices. As dawn breaks, the chilling realization of the cycle continues, with a reminder that there are only 364 days left until the next Purge.
