In a zany high-school game of "Killer"—where students must 'kill' each other using squirt guns—Matt Arnold finds himself on a mission to "eliminate" classmate Jenny Herk. He plots to catch her off-guard at her house, but fate has a more chaotic plan. Unbeknownst to him, real hit-men are simultaneously there to finish off Arthur Herk, who has been embezzling funds from Penultra Corp. The clash of these two worlds creates a comedic chaos that necessitates the involvement of police officers Monica Romero and Walter Kramitz, who respond to the bizarre scene.
As the situation escalates, Matt's friend Andrew reaches out to Eliot Arnold, Tim Allen, who also happens to be Matt's father. Upon his arrival, Eliot instantly feels an undeniable connection with Anne Herk, Jenny's mother, setting the stage for romantic entanglements. Meanwhile, a budding romance flourishes between Jenny and Matt, adding a layer of sweetness amidst the turmoil. In a quirky twist, the Herk family’s housemaid, Nina, unexpectedly falls for Puggy, a young homeless man living in a tree on their property, who heroically saves her from the danger unleashed by the hit-men.
In a turn of events that only heightens the absurdity, Arthur, becoming aware of the danger he faces, goes to an arms dealer to procure a rocket launcher but mistakenly acquires a suitcase nuclear bomb instead. Two escaped convicts, Snake and Eddie, unaware of the bomb's nature, conduct a bar heist that leads them to kidnap both Arthur and Puggy, taking the explosive device with them as they flee.
As Matt makes another attempt to "kill" Jenny in a mall parking lot, chaos ensues when a security guard misinterprets their squirt gun for a real firearm, prompting them to flee back to the Herk residence. The onslaught of confusion continues as Monica and Walter arrive only to find Eliot summoned once again amidst the pandemonium.
The convicts' crime spree reaches a peak when they force Arthur back to his home, capturing everyone inside, including Puggy and Jenny, and making their way to the Airport with the suitcase bomb. However, Nina cleverly escapes her hiding place and frees the others, but leaves Monica and Arthur handcuffed to a stereo. As the FBI agents tracking the nuclear device arrive, they manage to release Monica and instruct her to guide them to the Airport, leaving a delirious Arthur behind—lost in a hallucinatory state.
In a harrowing twist during airport security, the bomb is unintentionally activated, ticking down a 45-minute timer. Amidst the confusion, Puggy manages to get away during the boarding process. The FBI agents inform everyone that the aircraft must be downed if the bomb remains unaccounted for. In a stroke of luck, Puggy leads the group to the criminals' plane, where Eliot bravely infiltrates.
The criminals are eventually thwarted when Eliot uses a fire extinguisher as an unconventional weapon against Eddie and Snake. The case containing the bomb is hurled out of the plane, and despite Snake’s attempts to chase it, Eliot pulls a lever that disconnects the door, sending Snake plummeting into the ocean just as the bomb detonates safely in the water.
After the eventful day, Eliot receives accolades from the FBI and is promised rewards like presidential cowboy boots and a hat, with everything that transpired remaining classified.
The closing scenes reveal the fates of the main characters: Eliot earns Matt's respect, Anne and Eliot marry shortly after her divorce from Arthur, and Walter finds a new career as a male stripper post an embarrassing incident at the airport. The two hit-men, reflecting on their misadventures in Miami, claim the job was the lowest point in their careers, while Eddie ends up back in prison, befriending another inmate who shares his quirky humor. Arthur remains in a comically grim situation, still handcuffed and haunted by his own dog!
