Lieutenant Frank Drebin Jr. of the LAPD foils a gang of bank robbers while disguised as a schoolgirl, unaware they were covering up the theft of the “P.L.O.T. Device.” His reckless methods force Chief Davis to reassign him. While visiting his late father’s grave, Drebin asks for a sign of approval—an owl.

Investigating software engineer Simon Davenport’s death, Drebin suspects foul play after finding a matchbook tied to Simon’s employer, tech mogul Richard Cane. Cane reveals his plan to use the P.L.O.T. (“Primordial Law of Toughness”) Device to revert humanity into violent barbarians, preserving power for the elite. Drebin links the stolen device to Simon and learns Simon secretly met a journalist before being killed.

Suspended from duty, Drebin grows close to Simon’s sister Beth, even spending a bizarre weekend with her and a living snowman. After more missteps, Drebin captures Cane’s henchman, who reveals Cane will activate the P.L.O.T. Device at the New Year’s ball drop during an MMA fight.

At the arena, Drebin finds the Device inside the New Year’s balls. The crowd mocks him after an embarrassing wardrobe malfunction, and chaos erupts as the Device activates. Guided by his father’s spirit in owl form, Drebin defeats Cane, convinces Beth not to kill him, and uses the Device to restore peace. Cane is arrested, and Drebin reunites with Beth.

In a post-credits gag, “Weird Al” Yankovic performs in an empty bunker.