Penny is a little orphan girl, but has had no luck getting adopted. Her only friend at the orphanage is Rufus, the cat and her stuffed teddy bear. She is “adopted” by Madame Medusa and Mr. Snoops where she is put to work. They send her into a pirate cave to retrieve The Devil’s Eye, a large diamond.
Feeling hopeless, Penny sends messages in bottles asking for help. The Rescue Aid Society finds one of these bottles and send Bernard and Miss Bianca to help Penny.
The two mice comfort Penny, help her find the diamond and trap Madame Medusa and Mr. Snoops and the three escape on the Swampmobile.
At the end of the movie, Penny is adopted by real parents.