Deep in Devil's Bayou sits an old, rotting riverboat, where a lonely little orphan girl has been kidnapped by two money-hungry thieves. Medusa and her trusty sidekick named Snoops need someone small to go into the dark depths of Black Hole, where legend has it a priceless diamond was hidden in a pirate's skull. Now, Penny's only hope lies in a bottled cry for help that has been found by The Rescue Society, a group of mice determined to help anyone anywhere. It's a small girl and two smaller mice against a pack of thieves who have sworn to get their greedy hands on an extraordinary treasure ... no matter what. With just minutes to act, the clever trio are desperate to outwit their captors before all is lost ... before Penny's dreams of finding a loving family are buried in the merciless tide of Devil's Bayou.