In 1850, fifteen-year-old Jonas Abrams signed on with Captain Will Johnson to sail his fifty-seven-foot cutter, Wander, from the Chesapeake Bay to St. Thomas Island in the Caribbean Sea where Captain Will wanted to establish a boat repair business. For Jonas, this is the adventure of his dreams, but after five days at sea, they encounter a violent storm, giving Jonas his first acquaintance with rough water sailing, and creating doubts for him about adventures at sea.

Upon arriving to the islands, they come across an uncharted island where they encounter Swabbies' Revenge, a ship overtaken by mutineers. Even though the days of pirating in the Caribbean Sea are long past, she is flying the skull and crossbones and threatens Wander with a cannon shot across her bow to get out of their anchorage on this island.

Jalani and his men had mutinied, overtaking Captain Wilhelm Wagner and his ship, Captain's Bounty, renaming her Swabbies' Revenge and subsequently using her to plunder the cargo-hauling ships of the greedy plantation owners. Captain Wilhelm had been a cruel and abusive captain who had treated his crew, descendants of plantation slaves, as if they were slaves of his own.

While looking for Blackbeard's lost treasure on St. Thomas Island, Jonas and his shipmate, Spike, stumble upon crew members of Swabbies' Revenge guarding a cave. In time, they learn these men are hiding gold and silver in the cave. It is their shipmate, Benny, however, who foolishly decides to steal this treasure for himself, even though an ancient Indian woman warns him against doing so.