Eleven year old Marble Jones worked in his father's tavern. He listens in on the stories that the sailors tell, particularly of pirates and the legendary Ghostship Mathematica. When a genuine pirate walks in to the tavern one evening and gets involved in a barroom brawl Marble takes his opportunity to escape his violently abusive father and stows away on the pirate's ship.
On board the ship, Jones is discovered but is surprised that there are only two crew members, and that they don't try to send him back home. The pirate captain reveals that he stole a map during the brawl earlier that reveals the location of the Ghostship Mathematica.