When Sara Newton and Beethoven are sent to spend the summer with Sara's uncle, clumsy mechanic Freddy Kablinski (her mom's brother) in an old mining town called Quicksilver, the mischievous Beethoven "digs up" a clue to the whereabouts of the legendary, hidden fortune of two bank robbers named Moe and Rita Selig. Now everyone wants to be his best friend as his discovery unleashes a frenzy of treasure hunting among the community's creatures. With help from Uncle Freddy and a boy named Garrett, Sara and Beethoven try to help uncover a secret that has been in the crazy little town for years.