Gutterballs

Two groups of teenagers are allowed to bowl after hours at the Xcalibur Bowling Centre in Surrey. A tense confrontation erupts when Steve's group harasses Sam, and Jamie steps in to chastise them. Lisa breaks up the initial brawl by dropping a bowling ball on Steve's foot. Egerton orders everyone to leave and promises they can resume the tournament the next night.

That same night, Steve violently rapes Sam, a transgender woman, while Egerton is downstairs and unable to hear the commotion. The assault ends as Steve leaves and heads deeper into the building.

A.J. rapes Lisa on the pool table, and Joey participates in the abuse while Patrick is horrified but coerced into helping. Steve then returns with a bowling pin and presses Patrick to continue the assault. The four leave Lisa naked on the pool table.

The teams resume the tournament as the two groups arrive once more. Steve comes with Julia and Hannah, while Jamie returns with a traumatized Lisa. The game begins and Lisa heads toward the elevator; Patrick tries to apologize for his involvement. On the scoreboard a mysterious BBK marker appears, which the players dismiss as a glitch.

Dave meets Julia in the bar and they share a kiss. The unknown killer slips out of a bathroom stall and suffocates them both in a compromising position. After the murder, two strikes appear on the BBK scoreboard in the form of skull-and-crossbones.

Sam goes to the bathroom to 'freshen up' and is attacked when a stall noise draws her in. She is forced to swallow a bowling pin and is killed. Her body is castrated with a switchblade, and the killer chains the exit to trap the others inside.

Ben and Cindy have sex; Ben leaves to fetch a condom and is later found with his eyes gouged out by a sharpened bowling pin. The escalating violence shreds any sense of safety for the group.

Cindy upstairs is strangled by shoelaces; Hannah's head is crushed by a mechanical knight wielding two bowling balls. A.J. is killed by a fixed ball waxer in a grim, ritual-like sequence. The murders continue to mount.

In the pinsetters area, Steve discovers a headless Joey. The killer appears, and Steve tries to fight back but is bludgeoned with a bowling pin and killed in a brutal clash.

The killer returns with a shotgun and removes his mask to reveal Egerton as the perpetrator. Lisa arrives, revealing that she herself has murdered Steve, and Jamie is shown to be part of the plan. Egerton explains his motives, mentioning that Patrick was spared for reasons he will not disclose.

Patrick steps forward and confesses his involvement in the rape. Egerton acknowledges it but spares him for now, creating a tense moral imbalance among the survivors.

Lisa confronts Egerton, questioning why he killed everyone and why he spared Patrick. Egerton answers with a grim warning and then she slits his throat with Sam's switchblade, ending his reign of terror.

Jamie, realizing his own madness, wrestles Egerton in a brutal scuffle and finally blows his head off, ending the killer's immediate threat. The survivors reel from the chaotic revelations and the mounting casualties.

Sarah shoots Lisa to end her murderous rampage, bringing some sense of closure to the carnage. The group breathes a fragile sigh of relief as they brace for what comes next.

With all BBK killers dispatched, Sarah shoots the chains off the exit doors so they can escape. Suspecting Jamie did nothing to prevent the murders, Sarah turns the gun on him and kills him, sealing the collapse of their fragile alliance.