Jake was sent to the principal's office for dancing on top of the desks in Professor Rotwood's class. Jake was talking to Derceto about what happened in Rotwood's class. Trixie and Spud were listening through the office door. Jake said that Professor Rotwood was lying, but the cameras said otherwise. The principal then made Jake write a report on his role model, and Trixie and Spud suggested Grandpa.
Jake had to clean up the shop. Grandpa mentioned to Jake that he told him to clean the shop and give Fu Dog a bath. Jake said that the shop is so clean that you could eat off it, but there was some filth on the counter. When it was time to give Fu Dog a bath, Jake grabbed the vacuum cleaner and started vacuuming Fu Dog. But everything went wrong, and the vacuum exploded and got the shop even dirtier. Councilor Chang then arrived.
Since Jake didn't clean up anything, he had to stay in the shop while Lao Shi and Chang left on business. While Jake was cleaning everything up, he got mad and said that his grandpa is really uptight, but Fu Dog told him that he used to be like Jake when he was young. Fu Dog then showed Jake a book that contained everything that Fu Dog and Grandpa had lived through.
While Fu Dog was telling Jake about the times he had with Grandpa, Trixie and Spud came in and listened to the story, too. It turned out that Grandpa was the way he is now because of the Dark Dragon. While Jake cleaned, he thought about it and figured out that Chang set them up, and that Lao Shi was now all alone and Chang was trying to do the same thing 30 years later.
In the sewers, Jake saw Grandpa tied up. Lao Shi told him it's a trap, and then the Dark Dragon appeared and said, "A trap that appears to have worked!" Fu Dog told him that he wasn't going to faint this time, but Chang once again hit Fu Dog in the back of his head, knocking him unconscious. Chang told them why she betrayed them and joined up with the Dark Dragon. Jake said that he had human and magical creatures who got along really well, and they all engaged in battle. As they clashed, the Tooth Fairy kept the Dark Dragon busy with her Tooth Minions. While Trixie and Spud took care of Chang, Trixie and Spud captured Chang in a net. Jake grabbed Grandpa and fled. Chang told the Dark Dragon that they were escaping.
Outside, Jake and the Dark Dragon fought, but he dodged every blow thanks to the Oracle Twins that helped Jake. The Dark Dragon said, "Oracle Twins. Very resourceful, but you are no match for me!" When the Dark Dragon stepped on a piece of wood, Jake went up where everyone else was. The Oracle Twins, Trixie, Spud and Jake jumped off and catapulted the Dark Dragon away, where he landed near the rocks. The Tooth Fairy then came in with a bulldozer carrying large pieces of piled-up wood and smashed the Dark Dragon with them. The Dark Dragon disappeared in an explosion, and the gang celebrated their victory. Meanwhile, Fu Dog awakens expecting to fight, only to discover nobody is with him and the battle's already over.
In the principal's office, the principal was reading Jake's paper that he wrote about his Grandpa. The principal said, "You are really admiring your Grandpa." Jake responded, "Believe that. Starting from now, things are going to change, even between me and Professor Rotwood." Jake left dancing but didn't see Professor Rotwood and accidentally pushed him down the stairs. When he crashed to the bottom, Professor Rotwood yelled, "Jake Long! To the principal's office!" Jake replied, "Aw, man!"