Mel and Jules are best friends returning from a trip in Mexico. Seth and Matt join them on the same plane and introduce themselves after landing. Jules guides Mel to the bathroom to help with motion sickness, and Mel reveals she has just broken up with her fiancé. Mel’s luggage is lost, so she must return the next day to retrieve it.
Outside, they board a shuttle, and the driver, Driver, offers to charge them half the price. On board, they meet Andy, a shy family man. Seth and Jules flirt with each other as the ride unfolds. After a detour, a car forces the bus off the road, and the driver steps out to survey the damage, revealing a flat tire. Jules tries to call for help, but there is no cell service. Matt offers to help change the tire, but as his hand hovers over the tire, the jack collapses and the bus falls, severing his fingers. They hurry to the hospital, while the driver calmly pulls over and pulls a gun, taking everyone’s phones and wallets. Mel and Seth argue about taking action, and Jules finds a flare from the safety kit. Mel hatches a plan to open the window, but Andy notices the commotion and throws the plan into chaos. The flare is ignited, drawing the driver’s attention, who stops the bus and removes the flare.
The driver slashes Seth’s face with a knife as a warning and explains a “change of plans,” driving them to an enclosed ATM so Jules can withdraw money. Inside, Jules sets a paper fire to trigger an alarm. The driver rushes toward her, but she slams the door shut. Mel escapes, but the driver warns that Jules will suffocate if Mel doesn’t return. At a supermarket, Mel uses sign language into the CCTV to describe her plight and slips a note to the clerk to review the recording later. Seth manages to break free and make a run for it, but is ultimately run over by the bus.
Mel later shows Matt a knife she has hidden in an ice bag, which she uses to cut their belts. Matt uses the ice bag to smash a window, and they all shout for help. When the driver approaches with a gun, Mel cuts his wrist with the knife, and Matt knocks him out with a bag. Mel grabs the gun and threatens to shoot the driver, forcing him to hand over the keys to free Jules and Andy. Mel then drives the bus, with Matt and Andy watching the driver. Andy unexpectedly stabs Matt in the throat, revealing he’s in league with the driver. They stop at a bridge to dispose of the bodies, and then the driver torments the two women for a while before being persuaded to stop.
Mel retrieves a tire iron from beneath the seat. Andy tapes the women’s mouths and cuts a lock of hair. Mel fights back, striking Andy with the tire iron, and the driver is forced to halt. Mel seizes control, slams the brakes, and uses the weaponry around to incapacitate the attackers. The bus crashes into a wall during the ensuing struggle. Jules discovers Andy dead, and both the driver and Mel lie unconscious. She flags down a passing car, but the bus runs over that rescuer as she speaks with 911. The driver then drives the women to a warehouse, where he burns a tattoo from Jules’s body and empties the driving licenses to a drawer already full of IDs from kidnapped victims. He has Jules dye Mel’s hair blonde, then makes Mel and Jules strip down to their underwear and white high heels for inspection. The inspector—who is the same man who shoved them off the road earlier and who watched them at the airport—inspects their bags and finds Jules’s antifungal meds. Since Jules is no longer useful, both women must be in good health, so he takes her with the driver onto the bus and gasses her.
Mel threatens to cut Jules’s face with a shard of glass to make her useless, but eventually she stabs the driver in the leg and hits him with light fixtures. She finds the gun, loads it, and shoots him. Believing him dead, she tries to escape in the bus, but the driver comes to life again and traps her in a large wooden crate filled with Mel’s purchases: flashlight, bread, water, magazines, kitty litter, a litter box, and motion sickness pills. Trapped in darkness, Mel yells for help, and when a forklift arrives, she discovers the operator is part of the operation. The crate is loaded onto a cargo ship bound for Asia. Inside a photo on the crate shows seven young women, naked, blond, in white heels—hinting they were kidnapped and forced into sex slavery overseas. Mel stares in horror at the image. The crate eventually leaves for the voyage, and the final shot shows Mel’s lost luggage turning up at the airport the next day.
