An excerpt from the Introduction:

TWENTY-FIVE days after the appearance of "Religious Courtship," and forty-nine days after "Moll Flanders," Defoe published, on the 17th of March 1722, "A Journal of the Plague Year: being observations or memorials of the most remarkable occurrences, as well public as private, which happened in London during the last great visitation in 1665. Written by a Citizen who continued all the while in London. Never made public before."

Attention was drawn to the Plague of London by the public alarm at the plague at Marseilles in 1720-1. A very large number of books and pamphlets had been published on the outbreak at Marseilles and on the pestilence in general, and Defoe showed his usual skill in seizing upon a subject of general interest and using it for his own purpose. He had already written on this topic in the newspapers, and in the same year he published another excellent narrative of the Plague, which will be found in a later volume; and these works are all that can be said to have survived of the many which were written at this time. In fact, the popular knowledge of the Plague is derived almost wholly from Defoe.

Upon what, then, did Defoe base his narrative?

At the end of the volume appear the initials "H. F.," and it has been suggested that these may be the initials of one of the Foe family. We now know that Defoe had an uncle, Henry Foe, who was born in 1628, and may very well have been in London in 1665. We have no positive information as to what became of this uncle, but he had a sister Mary (of whom we know nothing); and Defoe interpolates in his story the following note: "The author of this journal lies buried in that very ground [Moorfields], being at his own desire, his sister having been buried there a few years before." Beyond this, we are told only that the narrator was a saddler, who lived, with a housekeeper, maid-servant, and two apprentices, "without Aldgate, about midway between Aldgate Church and Whitechapel Bars, on the left hand, or north side, of the street," and that he had an elder brother, who sent his wife and two children to Bedfordshire, and then followed himself. The brother who resolved to stay in London had friends and relations in Northamptonshire, "whence our family first came from," and an only sister in Lincolnshire.

The Foes came from Northamptonshire, but Henry Foe's elder brother died long before the Plague, and the facts, though curious, seem to suggest only that Defoe made use, for purposes of local colouring, of names which were familiar to him. He had himself been married at St Botolph's, Aldgate. Certainly there is nothing in the story to support the statement that it was written by "a citizen who continued all the while in London," unless that citizen be Defoe himself, whose mannerisms abound throughout the book.

The corrected date of Defoe's birth shows that he was about six years of age—not four, as previously supposed—at the date of the Plague; and if, as is very probable, his parents remained in London during the visitation, he would himself remember a good deal of the striking events of this terrible year; and as he grew up the matter would for long be the subject of conversation among those around him. There is mention on several occasions of a friend, Dr Heath, but this character seems to be imaginary, as no doctor of the name can be traced.

Apart from personal recollections and the talk of others, Defoe derived great help from books. He had in his library, "Necessary Directions for the Prevention and Cure of the Plague," 1665, and "Medela Pestilentiæ," 1664; but he also made much use of "London's Dreadful Visitation," 1665 (the weekly bills of mortality), the Rev. Thomas Vincent's "God's Terrible Voice in the City," 1667, and Dr Nathaniel Hodges's "Loimologia," translated by Dr Quincy in 1720. Defoe expressly alludes to Dr Hodges as "one of the most eminent physicians." Hodges, like Defoe, doubted the policy of shutting up infected houses, but, like Defoe, he gave arguments on both sides of the question. He deprecated public fires in the streets.

The "Journal of the Plague Year" is in some respects Defoe's masterpiece; and its realism, which is unsurpassed, caused Dr Mead, the eminent physician of the time, to refer to the book some years afterwards as an authority. According to his wont, Defoe places his story in the mouth of a sober citizen, who describes in his own fashion what he saw and heard around him, and the apparent simplicity of his style adds to, rather than detracts from, the awe-inspiring nature of the catastrophe. As might be expected from a man like the saddler, there are many figures and trivial details, with occasional repetitions; and sometimes the narrator expresses contradictory opinions, as is natural with one whose views respecting remedies or safeguards were modified by constant discussion with others....