For the Term Of his Natural Life: Summary

Here is the summary:

We follow the story of Richard Devine aka Rufus Dawes from his life in England when his 'father' (not actually his birth father) disowns him when he finds out he is a bastard child. Richard leaves home, vowing to never return, to save his mother from the shame of everyone finding out. By extreme bad luck he is, on his way from home, implicated in a murder (of his own biological father), tried and sentenced to transportation to a penal settlement in Tasmania.
By now he has hidden his identity, and gives the false name of Rufus Dawes.
From then on, life goes from bad to worse. He falls sick on the convict-crowded ship, and is later accused of leading a mutiny, which he actually helped avert. No one believes him when he pleads innocence. He is sent to Macquarie Harbour, with the worst of convicts, and is constantly punished for attempting to escape.

After a botched suicide attempt he finds himself left at Macquarie Harbour, which has been abandoned for Port Arthur. It so happens that Mrs Vickers, (whose husband is the commander of Macquarie Harbour) her child Sylvia Vickers, and Capt Frere get left behind too, when convicts seize the ship they were to travel in. Capt Frere is Richard Devine's cousin, but does not recognize him in the person of Rufus Dawes. Dawes comes across them, and joins their party and, inspired by the child Sylvia, he saves their lives. He builds the boat that sends them to safety, and he navigates when the jealous Capt Frere has given them up for dead.
When they are saved, Capt Frere turns on him, accusing him of attempting to murder them and attacking the child. He paints himself as the hero, saying he saved her life by giving her his own food, which is what Dawes actually did. The child is sick, and loses her memory, her mother is sick and dies. So Dawes has none to defend him, and is sentenced to life imprisonment. He believes Sylvia is dead.

Meanwhile Sylvia grows into a young woman, and having lost her memory, believes Frere to be her saviour, they are engaged to be married. The convicts who seized the ship and left them at Macquarie Harbour are arrested and put on trial. Dawes is brought up to identify them. When Sylvia sees him, she swoons and seems she will remember, but she does not, and upset, leaves. Meanwhile Dawes realises who she is, and tries to plead his innocence but she has left, and no one believes him.
He later escapes from jail, and comes to beg her to defend him, but she still does not remember. He thinks she has betrayed him, and gives up hope. He is sent to Hobart.

Meanwhile, John Rex, another convict escapes with the help of his once-lover, Sarah Purfoy. He is a spitting image of Rufus Dawes, and by luck has found out his true identity as Richard Devine. He escapes from Sarah, goes to England, pretends to be Richard, and lives the high life.

Dawes is at Norfolk Island years later, when Capt Frere becomes the new commander there, bringing with him Sylvia. She is unhappy, realising now that he is a rough, selfish and cruel man. The Rev North, chaplain of the Island, falls in love with her and proposes that they run away together. They are to leave on the same boat, Sylvia supposedly to go see her father. After Sylvia walks in on one of the warders torturing Dawes (on her husband's orders), she stops the torture and saves him. Frere is angry and strikes her.

The Rev North has been reaching out to Dawes, having been with him on two settlements, and he is the only chaplain Dawes has been open to, realising that he has a heart, and mercy. Rev North is an alcoholic. Dawes reveals to him the story of what happened on Macquarie Island, and begs him to tell Sylvia. He does not tell her because he doesn't want it to interfere with his and Sylvia's affair.

Meanwhile Sarah Purfoy finds Rex in England and threatens to expose him unless he tells Richard's mother she is Richard's wife. The mother, at the same time, decides to confront him with her suspicions that he is an impostor. He is confronted and bows, Lady Devine finds out that her son has been convicted for the murder, which John Rex actually commited. We find out that Lord Bellasis, whom he murdered was his father, therefore Dawes is his brother. Sarah takes Rex away, and he is found to have suffered a stroke on their way to Sydney.

On the night they are to sail, North comes back to confess his guilt to Dawes, but Dawes stops him, realising his plans with Sylvia. He then pours out his life story, begging North to spare Sylvia from doing wrong, and showing him how, through love, he has sacrificed much. North leaves confused. Meanwhile, the guard is drunk on alcohol that North gave him, and Dawes slips out in North's coat. He heads for the ship and it sails, thinking he is North, who is still on the Island. He hides himself, but that night a storm rises, and Sylvia comes to him.

She realises he is impersonating  North, but, at the same moment, her memory returns of how he saved her. And they hold each other as the storm rages.
We open the next day with their dead bodies floating out together to sea.