A former motorcycle gang member, Gi-su now earns his living as a bike messenger. One day after making a delivery to an office building, he witnesses the building blow up. Never suspecting he could have anything to do with the disaster, he moves on to his next job—which involves escorting a girl group singer, A-rom, to a TV station. As she puts his helmet on, a timer mechanism is triggered and a countdown clock appears. Gi-su gets a call from a stranger telling him that the helmet is booby-trapped and will blow up if he fails to make a series of deliveries within a fixed time limit. With the police hot on his trail, he races to complete the deliveries and stop the timer on the helmet.