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 is based on the escape of Alexander Pearce, who ate his companions during two different escape attempts from the Macquarie Harbour Penal Settlement on the West Coast, Tasmania.
Typical of Victorian-era convict novels, Rufus Dawes, is a wrongfully convicted gentleman. Under the prevailing morality of the time, a murderer would have been inappropriate for a hero in popular fiction.