Like so many urban legends, this one begins on a dark and stormy night. While there are more than a few variations on the story, like what number the route was, the story generally goes like this: A bus is traveling late at night, around midnight, and it's the last one of the evening. Two men flag down the bus, and even though the driver is reluctant to pick them up since they're not at a stop, he acquiesces and lets them on anyway. So far, so good.
But, it turns out, it's actually three men. The two are holding up another one who appears to be in rough shape. It also turns out that all three of them are extraordinarily pale, and wearing garb from the Qing Dynasty (which lasted from 1644 through 1911). The bus driver apparently explains it away by claiming that the three are actors who didn't have time to change after work.
As the bus slowly empties out, it gets down to a young man and an elderly person (which has been both a man or a woman, depending on the story). Out of nowhere, the older person picks a fight with the young man, claiming that he stole his wallet and forcing him to get off at the next stop to go to the police. Upon disembarking, they tell the young man that the fight was a ruse to help them get off the bus: apparently the three men on the bus hadn't been touching the ground. Some versions claim that the men didn't have legs at all. The two go to the police to report the alleged spirits, but get ridiculed.
However, the next morning they find out that the bus never completed its route. Some versions state that the bus was never found, while others claim that the bus was found days later with three severely decomposed bodies inside.