The Jinson twins, Joe and Debbie, decide to start a business during their summer vacation, hiring themselves out to do odd jobs. They find themselves in an odder job than they counted on when Mrs. Gray, who lives with her talkative parrot, the Captain, in an old house down off River Road, engages them to help clean out her basement. Aided by their friend, Mr. Benjamin, the proprietor of the Resource Recovery and Recycling Center (a.k.a. the junkyard), the twins use the clues that Mrs. Gray's late husband, a former sea captain, left behind to figure out, using scientific principles, where the captain hid his enormous collection of antique Spanish gold coins. But some other people know about the treasure too and have no intention of letting an old lady who spends most of her time with a parrot, an old man who runs a junkyard, and a couple of kids get the treasure.