An Italian merchant Marco da Cola comes to Oxford, where he makes friends and enemies, becoming involved with the community of natural philosophers and undertaking experiments with blood transfusion. He is treating the mother of the feisty Sarah Blundy, the daughter of a Leveller and now on the margins of society. But when a fellow of New College is poisoned, Sarah is an obvious suspect...
The first part of An Instance is da Cola's account of this visit to Oxford, written down much later, and the following three parts are responses to that, and to each other, by three other characters. The young Jack Prestcott tries to clear his father's name from the taint of treachery, while under attack by witchcraft. The mathematician and cryptographer John Wallis uncovers da Cola's real identity and is determined to bring him to justice. And the antiquarian Anthony Wood, eventually "cracks the code" and uncovers — perhaps — what actually happened.
The narrators of these stories are both deceived and trying to deceive, and have very different agendas. One is concerned for the truth but needs to conceal a great secret, one is driven by desire for revenge, under the shadow of madness, one is a blinkered fanatic, a misogynist and xenophobe, and one is a man in love. This makes for a journey with surprises, on shifting foundations. We are presented with four different candidates as murderer, for example, while our evaluations of different figures shift backwards and forwards, often quite abruptly.
A range of historical figures feature as characters, most notable among them the scientist Robert Boyle, Cromwell's spymaster John Thurloe, the philosopher John Locke, the cleric Thomas Ken, and the doctor Richard Lower. The historical background is worked into the story through the arguments of these and others, over religion, over politics, and over philosophy and the nature of knowledge. This was a period when all of these topics were fervently debated, so this can be done quite naturally. (The lack of any kind of artificial "background briefing" does mean that readers without any knowledge at all of the period may find parts of An Instance of the Fingerpost hard to get a grip on, though Pears includes some biographical notes in a brief afterword.)
The overall framing requires some suspension of disbelief, with the motivations of the four protagonists for writing down their stories not entirely convincing and their language and style not really different enough. Used just as a framework, however, this doesn't grate — and the trade-off is of course that the text actually works as a novel.
An Instance of the Fingerpost is vastly more ambitious than Iain Pears' earlier work, a series of seven novels about a detective with the Italian Art Theft Squad. It retains the pacing and drive of a good mystery, but adds a complex and original structure and historical and intellectual depth to make a striking and memorable novel.