Most of this book takes place during a long voyage of the Surprise from Australia to the Sandwich Islands. Clarissa Harwell, a convict with a dubious past, is discovered hiding on the ship. She was brought aboard by Oakes, a midshipman. Soon, most of the officers are in love with her, which causes a great deal of jealousy and inefficiency in the ship. Stephen befriends her and discovers that she had knowledge of high-placed officials in England that can be useful to British intelligence.

In the Sandwich Islands, Jack helps a chieftess defeat a neighboring tribe that was attacking her with the help of a French privateer. He also recaptures the Truelove, a British whaler that had been captured. Oakes, who has married Clarissa, is sent off in the prize, and Jack takes off after the privateer.