Since her Uncle Oscar passed away and left Rebecca his odd little antique shop specializing in Gold Rush history, her cat Rupert has sniffed out several tightly wrapped bundles of cash that Oscar had apparently hidden throughout his apartment. But now Rupert has turned up something else -- a dusty green vase with a toy bear inside holding a tiny paper flag that reads "Nevada City." Rebecca assumes that this is just another of Oscar's infamous clues to one of his valuable hidden treasures. Eager to put the pieces of the puzzle together, Rebecca heads to the former mining boomtown of Nevada City accompanied by her nosy neighbor, Monty, and her cats. But instead of finding another clue, she finds her uncle's oldest enemy waiting-- and he has no good intentions whatsoever.