Charlotte is a thirteen-year-old American girl accustomed to wealth, privilege, and strict social rules. Returning home to Rhode Island after attending school in England, she finds herself unexpectedly alone on a merchant ship. Raised to respect authority and good breeding, she initially gravitates toward the captain while feeling uneasy around the rough crew.

Zachariah is the oldest member of the Seahawk crew and the only Black sailor on board. He acts as the ship's cook, surgeon, carpenter, and preacher. Weather-worn and dressed in rags, he is perceptive and gentle, recognizing that both he and Charlotte are unique outsiders on the ship.

Captain Andrew Jaggery commands the Seahawk with rigid discipline and an expectation of high profits. He presents himself to Charlotte as a refined gentleman, sharing her appreciation for manners and order. However, he treats his sailors with extreme harshness, believing that fear is necessary to prevent laziness.

Mr. Grummage is a fussy, hurried business associate of Charlotte's father. Tasked with ensuring she boards the Seahawk, he is strictly focused on his schedule rather than her comfort. When the other passenger families cancel, he insists she board anyway to fulfill his employer's instructions.

Mr. Keetch is the scruffy, agitated second mate of the Seahawk. He moves with a cringing servility when summoned by the captain. His uneasy demeanor and loud warnings to Charlotte mark him as a deeply anxious officer who fears the tension brewing on the vessel.

Roderick Fisk is a powerful, lantern-jawed sailor aboard the Seahawk. He habitually keeps his large fists clenched, giving him the appearance of someone perpetually ready to brawl. Like the rest of the crew, he works under grueling conditions and harbors deep resentment toward the ship's leadership.

Mr. Hollybrass is the first mate, identifiable by his red face, slight stoop, and powerful shoulders. The only crew member who has not sailed with the captain before, he relays orders with a raspy voice and perpetual suspicion. He remains watchful and silent, carefully executing commands.

Cranick is a former sailor who lost his arm after a severe punishment ordered by Captain Jaggery. His mistreatment is the central reason the current crew despises the captain. He operates in the shadows, representing the crew's desire for justice and retaliation.

Charlotte's father is an American executive for a cotton-goods company. Having recently received a promotion, he returns to Providence, Rhode Island, leaving his daughter to finish her schooling in England. He demands punctuality, proper spelling, and strict adherence to class expectations.

Charlotte's mother accompanies her husband and younger children back to Rhode Island. She represents the high-society expectations placed upon her daughter and aligns closely with her husband's strict standards for their household.

Ewing is a young, Scottish sailor working aboard the Seahawk. He endures long, hot days tarring the rigging and performing other exhausting duties. His need for a simple sewing needle inadvertently leads Charlotte toward the crew's hidden activities.

Barlow is a sailor on the Seahawk who acts as a messenger for the crew's concerns early in the voyage. He quietly warns Charlotte that her presence on the ship will lead to no good, demonstrating the crew's collective anxiety about the impending journey.

Dillingham is a bearded, bald, and barrel-chested sailor. He keeps a close eye on the ship's happenings and is highly observant of Charlotte's actions, particularly her possession of weapons.

Morgan is one of the deckhands who harbors intense resentment toward the ship's command. He communicates the crew's hidden threats through sharp, wordless gestures when he suspects they are being watched or betrayed.

Foley is a sailor aboard the Seahawk who shares the crew's deep-seated anger. He maintains a watchful, silent presence on deck, staring down anyone who might interfere with the sailors' objectives.

Grimes is a seasoned sailor aboard the merchant brig. He understands the lethal dangers of the sea and the necessity of proper physical skills, representing the rough, practical knowledge of the working-class seamen.

Johnson is a crew member who distinguishes himself by abstaining from the sailors' secret agreements. His refusal to sign the pact sets him apart from the collective anger of the rest of the crewmen.