Mikey finds himself in a strange and unfamiliar place after a magical ride off the rocket ship slide at the park. He soon starts to explore and meets a boy from this underground world, and they become friends. The boys spend the day playing and exploring before Mikey returns home back above the ground. Mikey awakes the next morning, thinking that he is remembering a dream but soon realizes that he is not dreaming, and he makes plans to return to find this world under the ground. He remembers that he was on the rocket ship slide when he ended up in the underground world. He plans a return to find Ukie and meets Bixie while trying to locate Ukie. Bixie tells him about his missing son, Rixie, and that he thinks that he has gone aboveground and that something has happened to him. Bixie asks Mikey to look for his son, and he agrees to help. After Mikey finds Ukie, he tells him about meeting Bixie and how he agreed to try to find his son. Mikey and Ukie devise a plan to find Rixie and the adventure soon begins. Will the boys find Rixie, and what more will happen during their adventure together?
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