Trollope was influenced in writing the book by The Old Law, a 17th-century tragicomedy written by Thomas Middleton, William Rowley, and Philip Massinger which he had read, and commented upon, in 1876.

[2] The Fixed Period is set in the year 1980 in the Republic of Britannula, a fictional island in the vicinity of New Zealand, and deals with euthanasia as a radical solution to the problem of the aged.

When a proposal was made to terminate citizens' lives at a fixed age to spare them undignified suffering and to help cut down on the state's expenditure on unproductive people, it got an overwhelming majority.

Born in 1913, he emigrated from New Zealand when he was a young man and was instrumental in building the new republic as one of a group of similar-minded men which included his best friend John Neverbend, ten years his junior, who is now serving his term as President of Britannula.

When all of a sudden Crasweller starts lying about his age and claiming that he was in fact born a year later, Neverbend realises that measures must be taken to ensure the smooth execution of the Law.

However, he soon finds out that it has dawned on other elderly citizens as well what the state has in store for them, and that various individuals have come up with all kinds of excuses and plans as to how they are going to oppose their deposition and, eventually, departure.

But despite this setback, and although both his own son Jack and his wife Sarah turn against him, Neverbend, who has long since passed the point of no return, considers it his duty as President and law-abiding citizen to have Crasweller deposited.

They have arrived on a warship of enormous dimensions and, by threatening to destroy the whole city with their "250-lb swivel gun", compel Neverbend to release Crasweller and eventually to step down as president.

[5] In the field of transportation, generally, the absence of any airborne vehicles is quite striking: when the British cricket team travels to Britannula they do so on a steam ship, and it takes them several weeks to reach their destination.

In telecommunications, apart from the above-mentioned "hair telephone," "water telegrams" and a "reporting-telephone apparatus" – all of which were only slight refinements of pre-existing Victorian technology – seem to be the only important inventions.

[6] The concept of mandatory euthanasia for humans after a "fixed period" (often 60 years) became a recurring theme in 20th century imaginative literature — for example, Isaac Asimov's 1950 novel Pebble in the Sky.