Black Jack and Pinoko go to visit a remote island and end up meeting a fisherman and his son. The fisherman wants his son to grow up and go to school, but when his son hears him talking about enrollment he runs away. After hours of searching, Black Jack finds him trapped by a huge clam. attempting to free the boy, Black Jack dives underwater and ends up getting stuck himself. After nearly drowning, Black Jack and the young boy are both free and not badly injured, but in the process Black Jack broke his arm.