NOTE: This spoiler was submitted by Jeremy
Four friends - Pat (Anton Yelchin), Sam (Alia Shawkat), Reece (Joe Cole), and Tiger (Callum Turner) - wake up in their van. They're part of the punk rock band The Ain't Rights. They slept all night with the engine on. Pat and Sam ride a bike to a nearby parking lot and siphon some gas to get them back on the road.
The band meets up with a guy named Tad (David W. Thompson) for an interview in his apartment for his radio program. He asks the band what their "desert island band" would be. Reece, Sam, and Tiger think of theirs, but Pat can't. After the interview, the band plays a gig, but their pay is barely decent split between the four of them. Tad tells the band that he got them to do a gig in a spot where his cousin works, and that the pay is better.
The band arrives at the venue, which happens to be a skinhead bar. They meet Tad's cousin Daniel (Mark Webber). The managers misspelled the band's name as "The Arent Rights". They go up to play a cover of "Nazi Punks Fuck Off", which doesn't go well with the crowd. They then play a different song, which doesn't get a much better reception.
After the show, the band gets their money and are about to head out. Sam forgot her phone in the green room, and Pat goes to get it. When he enters, he sees two people, Werm (Brent Werzner) and Amber (Imogen Poots), standing over the body of Amber's friend Emily, dead with a knife in her head. Pat freaks out and runs out of the room while calling 911. Two bouncers, Big Justin (Eric Edelstein) and Gabe (Macon Blair), force Sam, Reece, and Tiger into the room. Their phones get taken away while Justin holds them all at gunpoint.
Gabe gets two young skinheads together to stab each other in response to the 911 call as an officer arrives. The club's owner, Darcy (Patrick Stewart), arrives, and he says the band has to be dealt with.
The band attacks Justin and take his gun, with Reece pinning him down and threatening to break his arm. They let him up and Reece holds the gun at him this time. The club experiences a power outage, inciting a brief panic among the group until Amber turns on her lighter and sparks up a cigarette, which she gives to Justin and tells the band to watch the cherry in case of anything suspicious. The lights then go back on.
Darcy stands outside the green room to calmly discuss with the band on how to handle the situation. They agree to hand over the gun but keep the bullets. Pat still remains suspicious as Darcy says the cops have come and gone. Pat gets ready to hand Darcy the gun outside the room, as Darcy claims there is nobody else with him. This proves to be a lie when Amber sees another pair of feet through the vents. Before she can warn him, Reece tries to attack Darcy with a rod while Pat's arm gets slammed and cut up horribly. Reece pins Justin back down and snaps his arm, then places him in a chokehold until he passes out. Amber finishes him off by cutting him open with a box cutter.
While Darcy and the skinheads plan to get rid of them, the group starts to break through the floorboards for a way out. This leads them to a bunker where the skinheads run a heroin operation. There's no exit down there, so the group returns to the room. Tiger helps wrap Pat's arm in duct tape. With no other options, the group plans to make a run for it while arming themselves with some kind of weapon. Tiger and Reece run out, but Tiger gets his throat ripped out by a pit bull, and Reece gets stabbed to death.
Pat, Amber, and Sam have to stay in the room. Daniel and Gabe go to the room, where Amber tells Daniel that Werm killed Emily when Werm learned that Emily was going to run away with Daniel, and now Darcy is going to pin her murder on the band. Daniel guides the three downstairs to get some guns, but Daniel gets a buckshot to the face, courtesy of a skinhead. Pat kills the skinhead with a machete. The three run outside with a shotgun, facing the skinheads. Darcy tells them not to shoot at Amber. Sam gets shot in the leg and is then mauled by the pit bull.
Pat and Amber go back to the room, now both frightened and tired. Pat tells an anecdote about a paintball tournament he participated in, which he compares to his current situation as he was outnumbered in both scenarios. He and Amber then come up with a plan to survive.
Darcy sends two skinheads into the green room to kill Pat and Amber. They find Pat yelling nonsensically, now with his head shaved and his face with black paint on it. He hops into the bunker, and one skinhead follows. The other skinhead sits above keeping watch, unaware of Amber hiding in the couch. She crawls out and slits the skinhead's throat with the box cutter. The first skinhead looks for Pat with his shotgun. Amber distracts him by throwing the bodies of Emily, Justin, and the second skinhead down. Pat seizes the chance to grab the skinhead's gun, but they fight for it. Amber descends with the gun of the skinhead she killed and shoots the other one dead.
Gabe goes to the room as Pat and Amber make their way back up. Remorseful for what's happened, he says he wants to go to jail. Pat and Amber force him out of the room with their guns pointed at him. They leave the club as the morning comes. They leave Gabe to find a phone while Pat and Amber go into the woods.
The two come across Darcy, along with two other skinheads, trying to dispose of Sam, Tiger, and Reece's bodies, trying to come up with another story while also planning to blow up their van by putting a burning rag in the tank. Pat and Amber find them and shoot the henchman. Darcy attempts to walk away as he draws his gun, but he is shot dead as well.
Pat and Amber sit down as they wait for the police to arrive. They spot the pit bull, who walks calmly and lays by his owner (the dog got shot earlier and was given a sedative to allow him a little more time to live). Pat then tells Amber he figured out his "desert island" band. Amber says to tell someone who gives a shit.