After his adopted son Jimmy Boy is released from prison, mob boss Sosa and his crew celebrate with a high-energy night of partying. Among them is Nick, a hard-edged loan shark whose wife Alice is having an affair with his fellow gangster Mike. Not wanting to kill anymore, Mike contemplates leaving Sosa’s organization, but he still agrees to help Nick on a dangerous job. Following Nick’s orders, Mike tries to chloroform a man he discovers is Nick himself, and he learns that the Nick who hired him is from the future, while the present-day Nick slips away.
Mike soon realizes he has been framed as the informant who betrayed Jimmy, and he becomes the target of “The Barron,” a cannibalistic assassin hired by Sosa. [Future Nick] explains that six months from that night, he attempted to collect a debt from Symon, an inventor and friend of Alice who borrowed money to build a time machine. When the device is triggered, Nick is sent back in time to the night Mike would be killed, inadvertently shooting Symon dead and destroying the machine. While Sosa, Jimmy, and their men revel in a string of parties, [Future Nick] and Mike manage to recapture Present Nick at a convenience store and bring him and Alice to Nick’s secret apartment.
Both Present and Future Nick are aware of Mike and Alice’s relationship, and they acknowledge the troubled state of their own marriages in a lighthearted dig about Gilmore Girls. Revealing that Alice is pregnant with Mike’s child, Future Nick is determined to save Mike. He lies to Sosa, claiming he has captured Mike, and lures the Barron to the apartment for an ambush. Present Nick tries to reveal the plan, but is struck with guilt when the Barron seemingly kills Mike; however, this is only a ruse: the “assassin” is actually Chet, a special effects artist recruited by Future Nick to dissuade Present Nick from seeking vengeance.
The real Barron arrives and is shot dead by Future Nick, while Alice disables his henchmen with their own grenade. Future Nick tells Sosa that Mike has killed the hitmen and gone on the run, but Sosa vows to unleash his entire organization on him. With the true identity of the informant unresolved, a beloved but now dead gangster, Mike and the others prepare to take down Sosa and all his men at Jimmy Boy’s final party.
They plant weapons through the party with the help of a corrupt officer named Sam, and a fierce showdown ensues as Present and Future Nick and a reluctant Mike wipe out Sosa’s gang. Sosa is killed by Alice, but Present Nick is shot in the neck by a dying Jimmy. The group frantically tries to keep him awake as they sing along to Oasis’s “Don’t Look Back in Anger,” but Nick succumbs before reaching the hospital. In the aftermath, Alice reveals that Symon built another time machine, and Mike activates it to give Nick a second chance.
