Structurally, For the Term of His Natural Life is made up of a series of semi-fictionalised accounts of actual events during the convict era, loosely bound together with the tragic story of its hero. Most of the incidents and many of the individual characters are easily identifiable from historical sources including Marcus Clarke's own non-fiction work Old Tales of a Young Country. The plot illustrated below is based on the escape of Alexander Pearce, the notorious "Pieman", who ate his companions during two different escape attempts from the Macquarie Harbour Penal Settlement on the West Coast, Tasmania.
The story starts with a prologue, telling the tale of young British aristocrat, Richard Devine, who is the son of a shipbuilding magnate, Sir Richard Devine. In an incidence of domestic violence, Richard's mother reveals to Sir Richard that his son was fathered by another man, Lord Bellasis. Sir Richard proceeds to threaten the mother's reputation if Richard does not leave and never come back. He leaves him to pack for a while, claiming that he will fetch his lawyer to alter his will, so that Richard receives no inheritance. When Richard leaves, he comes across a murder scene: his biological father, Lord Bellasis has been murdered, and Richard witnesses Sir Richard walking away from the scene of the crime. The police come and lock up Richard, who now gives his name as Rufus Dawes (which is used for the remainder of the book), for the murder of Lord Bellasis. Additionally, Sir Richard returns home and dies straight away, possibly of a heart-attack, without altering his will. Rufus Dawes/Richard Devine never finds this out. Rufus is found guilty of the murder and sentenced to transportation to the penal colony of Australia. (Plot summary to be continued)
Among other dramatic events in the novel that are based on true events, a group of convicts escapes from the Port Arthur penitentiary. Getting lost in the wilderness, lacking survival skills and soon running out of food supplies, the men begin to starve and end up cannibalising each other. The last one remaining, Gabbett, is found on a beach by the crew of a whaling vessel, with the half-eaten arm of one of his comrades hanging out of his swag.