In 1787, in London's Newgate Prison, convicts Hugh Tallant, Ned Inching and Thomas Oakley are selected to sail to New South Wales as part of a new program designed to alleviate overcrowding in British prisons. While boarding their ship, the Charlotte , Hugh, an American, catches the eye of Sally Munroe, one of many female prisoners. When two sailors begin fighting over the feisty Sally, the ship's captain, Paul Gilbert, intervenes, then doles out harsh punishment for the seamen and 3rd Mate Spencer, the officer in charge of the deck. Before sailing, Hugh is introduced to influential convict Nick Sabb, a former London fence who uses his wealth to bribe the guards and sailors. Producing a recent London broadsheet, Sabb reveals to Hugh, who was convicted of highway robbery along with Thomas and Ned, that he has been exonerated by his great-uncle in Maryland, whose money he was accused of stealing, and is to receive a royal pardon. With Sabb's help, the shackled Hugh is allowed to speak with Gilbert and explains that he robbed his London agent only because the agent had been stealing funds sent by his great-uncle to finance Hugh's medical training. Although Gilbert believes Hugh's story, he refuses to delay departure until the pardon arrives. Gilbert then gives Sally, a former actress accused of theft, her own quarters, without shackles, on condition that she "behave." On his way back to the brig, Hugh knocks his guard out and jumps overboard, but soon is re-captured. As punishment, Gilbert has Hugh flogged fifty times and salt rubbed in his wounds. Later, Hugh offers Sabb, Thomas and Ned £1,000 to help him escape during a scheduled stopover in Rio de Janeiro. Sally, meanwhile, learns from convict Rev. Thynne, a victim of religious persection whom Gilbert has befriended, that Phillips, the governor of New South Wales, has enacted a law giving land to married couples. Sally immediately thinks of Hugh and asks Thynne to use his influence with the captain to procure the ship's surgeon post for Hugh. Later, Hugh offers to look at Spencer's arm, which has been broken, but Spencer, not wanting to act improperly, declines. Sally then tells Hugh that Gilbert has agreed to name him ship's surgeon, but Hugh refuses the position, insinuating that Sally compromised herself to obtain it. Hurt, Sally slaps Hugh, and later, the other female prisoners, angry over Sally's favored status, start to brawl with her. Gilbert again breaks up the fight and reprimands Spencer for not controlling the prisoners. In his quarters, Gilbert tries to seduce Sally, and when she resists, threatens to send her back to England. In response, Sally declares that she is friendly with Gilbert's rich brother-in-law and will expose Gilbert's lechery to his wife unless he leaves her alone. That night, at Spencer's request, Hugh resets the officer's broken arm and reveals his escape plan. Later, young Nat Garth, who has been imprisoned with his mother Nellie, is caught trying to return a compass that an older convict stole from Gilbert's quarters and is sentenced to solitary confinement. While secretly visiting Nat, Hugh notices that another prisoner has collapsed, but before he can examine him, a guard declares the sick man has the plague and agitates the other sailors to confront Gilbert. When Hugh then reveals that the man merely has scurvy, Gilbert angrily relieves Spencer of his duties. Then, shortly before they are to dock in Rio, Gilbert accuses Spencer and Hugh of plotting Hugh's escape and hints that someone has betrayed Hugh. Gilbert cancels the stopover and sends Hugh and Spencer to solitary confinement. Later, during a severe storm, their cells, along with Nat's, are flooded, and Nat dies. A grief-stricken Nellie stabs Gilbert, but only slightly wounded, the captain shoots and wounds Nellie, then orders her hanged. As they are now near Cape Town, Hugh, no longer in solitary, decides to go ahead with his escape and has Sabb hide Nellie in one of his rum barrels, hoping to trick Gilbert into thinking she has fled with him. Accompanied by Spencer, Hugh takes off in a longboat, but soon discovers that the Charlotte is following. After Hugh and Spencer are caught, the sadistic Gilbert commands that they be keelhauled. Spencer dies, but Hugh survives after Thynne intervenes and threatens to report Gilbert to the governor. When the ship finally reaches New South Wales and docks in Botany Bay, Thynne and Gilbert, who has uncovered Nellie's hiding place, discuss the convicts with the governor. Phillips decrees that both will have fair trials, but Hugh must work at hard labor in the meantime. While Hugh begins planning another escape with Thomas and Ned in the rock quarry, Gilbert tries to interest Sally in returning to England with him. When Sally refuses, Gilbert deduces that she is pining for Hugh and plots with Sabb, the traitor, to force Hugh to return to England. Gilbert informs Phillips that, by law, Hugh must return to England to face mutiny charges. Sure that Gilbert intends to kill him, Hugh tells Thomas, Ned and Sabb that they must escape that night, but Sabb leads the men into a trap on the beach. Before Gilbert and a group of armed marines can claim victory, however, aboriginal warriors attack, and Gilbert is speared to death. After Sabb runs away, the convicts and the marines fight the natives, eventually chasing them off. Hugh then discovers that some of the marines have the plague and orders their ship quarantined. Hugh cures the men, and Phillips later grants him and the other Botany Bay convicts their freedom. After Hugh reveals his desire to stay in New South Wales, he and Sally look forward to a happy future together.
