Mark is mocked at school and on the school boat when he is the only child in his class that didn't bring in an Indian artifact for show and tell. He decides to go to the private island of Willie Sam Gopher to find his Seminole artifact. Mark befriends Willie's son Jimmie Boy, who wants to go to school so he and Mark sneak off the island. The next day Mark introduces Jimmie Boy as his 'artifact'. Willie comes into the classroom and grabs Mark but is scared off by Ben. Ultimately Willie agrees to allow Jimmie Boy to attend the school.