Angus visits his twin cousins on Cape Cod for the summer. Soon after his arrival, they allow him to help search for Captain “Black” Sam Bellamy’s treasure hidden 300 years ago. They unlock seven clues on the seven gold coins minted by the pirate. Deciphering the clues requires intellect, courage, and an ability to work together to outmaneuver a crafty, old seaman named Tarts who tries to steal the treasure for himself. When the cousins discover the final clue site, a skull and crossbones created by shadows made when the sun sets, they again outmaneuver Tarts to retain Bellamy’s plunder.