Over the course of their journey to the West, San Zang's three disciples have time and again shown personal qualities that make them worthy of their master. But Sun Wu Kong, Zhu Bajie and Sha Wu Jing have been known to cause an awful lot of trouble. Now, the four companions must atone for vulgar bit of mischief by taking part in a seemingly endless competition of wits, and anything less than victory would mean losing more than just the contest.

The latest creature to hear about the group is the Alligator Demon of the Black River. He is the nephew of the King of the West Sea who recently ransacked the palace of the river's king and claimed it for his own. He disguises himself as a boatman who will help San Zang and his disciple cross the river. When he gets halfway down the river with San Zang and Zhu Bajie in his boat, the demon makes his identity known and kidnaps the monk and the pig, taking them to his palace deep in the water. Sun Wu Kong, the most powerful of San Zang's disciples, cannot understand how he was unable to detect the monster's disguise, as he has been able to do throughout their journey. Meanwhile, Sha Wu Jing plunges into the water to find his master and his elder brother. He finds the palace and calls out the Alligator Demon, but the foe proves to be too strong...