Marty and Susan Campbell are a small town couple visiting a large, somewhat unfriendly, declining northern city. They accidentally get lost and stranded in a deserted, rundown neighborhood after dark when Marty gets the wrong address for meeting a business client and are both left behind by a cab that drops Susan off after dark from shopping and whose taxi business requires callers to have business names and phone numbers before sending any cabs after dark. The parking lot that their rental car is in is locked between 7:00 P.M. until 6:00 A.M., leaving them unable to retrieve it before then as they didn't come back until after 7:00 P.M.'s closing time. After Marty barely escapes getting hit by a newspaper delivery truck, they both find a nearly deserted apartment building but no phone to use. Marty and Susan go back to the locked parking lot to try to get their rental car to drive back to their hotel. When Marty climbs the fence, two Dobermans attack him and he drops the car keys and barely escapes with his life. Marty calls the police from an outdated payphone that still requires coins to obtain a dial tone for emergency calls to try to get help but is told that since he trespassed on the locked parking lot, he can't file a complaint. Susan wanders away and is seen by a gang in a neighboring alley and runs back to Marty, who the police hung up on. They're chased through another alley and barely escape again. Marty finds another payphone that also needs coins for emergency calls and tries to get help again, but the gang leader catches him, forcing the usually non-violent Marty to fight back and he and Susan barely escape again. They hide in an abandoned theatre but flee when they find a corpse. Then they find a man and try to offer him money to drive them to their hotel, but the man is scared off. Next, they find an unstable derelict who sends Marty on a wild sewer chase to a non existent police station. Marty and Susan leave the derelict and wander down another rundown, empty street, where Marty breaks a store's windows in frustration over the lack of police response, setting off its alarms. They are sent to a subway by an untrustworthy street kid only to find it locked, but also find a burglarized church that was vandalized by the gang and sneak into through its broken door. They find an incapacitated junkie whose also-druggie sister thinks they're inside a hospital and that Marty is a doctor. Another gang member appears, giving the sisters directions to another subway to get home, which Marty and Susan overhear while hiding, meaning that both of these girls are members of this gang. Marty's watch has stopped and they find the subway's revolving gate locked to them but manage to squeeze in just as the gang finds them again and chases them through the subway. Marty drives the E-train while the gang enters the train and pulls the cord to stop it. Marty and Susan abandon the train, Susan is sent to hide while Marty lures the gang into another tunnel, where he knocks a pile of rubble onto three of its members and lures its leader into the boiler room, blinding him with steam and knocking him out with a large wooden board. He goes back above ground and finds Susan telling a policeman about their ordeal, who ironically, says "Glad to be of service" to a disgusted Marty. They go to their hotel to get cleaned up and change their clothes, return to the parking lot to retrieve their rental car and drive away after paying a $5.00 overnight fee to its attendant that found its keys but has no change if they didn't have the exact amount. The attendant tells them to be more careful next time and Marty and Susan drive off towards home.
