The Tree Stump Kid named Dave is disappointed because his friends Yin and Yang missed his birthday party. To make up for it, Yin and Yang promise to do anything to make it up to Dave. When Dave learns he has a "Day After His Birthday Party" coming up, he convinces Yin and Yang to pretend to be his students. But Master Yo warns Yin and Yang that no good can come out of lying. / Years ago, Master Yo gave a powerful weapon, the Knuckles of Infinite Smackdown, to a friend for safekeeping. But now that The Night Master is after it, Master Yo must take Yin and Yang on a road trip to try to throw The Night Master's lackeys off Master Yo's trail.