GUTTERBALLS

On January 1, 2008, at the Xcalibur Bowling Centre, a disco-themed bowling alley in Surrey, British Columbia, Egerton, the janitor, has allowed two groups of teenagers to bowl against one another after hours. After Steve and his friends Joey, Patrick, and A.J. harass Sam, a transgender woman, they are chastised by Jamie. A brawl then ensues between Steve's team and Jamie's. Lisa breaks up the fight by dropping a bowling ball on Steve's foot. Egerton tells the teenagers to leave and they can continue their tournament the following night.

Having forgotten her purse, Lisa heads back in. Inside, Steve proceeds to violently rape her. Egerton, downstairs, is unable to hear the commotion. Afterwards, he leaves. A.J. rapes Lisa on the pool table, then Joey abuses her. Patrick, horrified, refuses to participate. Steve returns with a bowling pin and prepares to insert it into Lisa before Patrick intervenes. Steve retorts by giving Patrick the pin, making him do it. He refuses at first, but is coerced by Steve. The four leave her on the pool table, still naked.

The following night, the two groups arrive at to continue. Steve is accompanied by Julia and Hannah. Jamie arrives with a traumatized Lisa. The teams begin, with Lisa leaving to the elevator. Patrick enters, apologizing. During the game, the players notice a mystery player on the scoreboard, BBK, but believe it is just a glitch. Dave meets Julia in the bar, and the two then makeout in the bathroom. The unknown killer exits one of the stalls while Dave and Julia are in the 69 position and suffocates them both. After this, two strikes appear next to BBK's scoreboard in the form of a skull and crossbones.

Sam goes to the bathroom to "freshen up." Frightened from a noise in a stall, she approaches and is then pulled under. They shove a bowling pin down her throat, and using Sam's switchblade, they castrate her. After, they chain up the exit. Lisa rejoins the group. Ben and Cindy have sex; Ben leaves to get a condom. Joey fixes the lane's pins. In the bathroom, Ben gets his eyes gouged out with a sharpened bowling pin. A.J. notices the increasing BBK strikes and questions Egerton about it; he says it's a glitch. Egerton then sends him to put a sign on a ball waxer that Joey broke earlier. Cindy, upstairs, gets strangled by shoe laces. Downstairs, a drunken Hannah searches for Julia. Her head is then crushed by a mechanical knight wielding two bowling balls. A.J. turns on a surprisingly fixed ball waxer, then is forcefully killed by it.

Annoyed, Steve goes behind the pinsetters to find a headless Joey. The killer appears; Steve tries to fight, but is bludgeoned with a bowling pin, then sodomized. The killer bashes his head in. Sarah and Jamie try to resume the game. Joey's severed head rolls out of the ball return machine. Both try to escape to no avail. They run and hide in the basement, where they find everyone's bodies.

The killer appears with a shotgun, then removes their mask to reveal Egerton. Lisa enters, revealing she murdered Steve. Jamie was included in the plan too. Lisa asks Egerton why he killed all her friends, to which he explains they had not helped, despite them not knowing. Another killer, Patrick, enters. He confessed his involvement in the rape to Egerton, who spared him. A furious Lisa berates Egerton for letting him live, to which he slits his throat with Sam's switchblade. Jamie, realizing his insanity, wrestles Egerton and, after a scuffle, blows his head off. Lisa sulks over her father, then grabs the switchblade and tries to attack Jamie. Sarah grabs the shotgun and kills Lisa.

With every "BBK" (Bowling Bag Killer) gone, Sarah shoots the chains off the exit-doors so the two can escape. Unsettled at Jamie for doing nothing to prevent the murders, Sarah turns the gun on him and kills him.