Mike Walsh and his cousin Kate Hopkins are excited to spend a summer night at Angel Stadium in Anaheim. Before the game, they explore a special exhibit about Gene Autry, the famous singing cowboy and original owner of the Los Angeles Angels. One display features a priceless gold record of "Rudolph the Red-Nosed Reindeer."But in the ninth inning, disaster strikes when the Angels give up a crushing grand slam. Fans wave their fuzzy "Rumble Monkeys" to spark a rally, until chaos erupts when a real monkey races onto the field, dodging players and even stealing a bat. The rally fizzles, and the Angels lose.Then an even bigger mystery is revealed: Gene Autry's gold record has vanished from its locked case. With help from Riley Autry, a country singer, Mike and Kate investigate. Their search leads to a nearby theme park, where they uncover clues about the monkey and soon discover the truth behind the theft.In the end, the record is recovered, the culprit is caught, and the Angels get another shot at a magical monkey-powered rally!