The novel begins with a deadly explosion in the office of a successful mathematics professor at a midwestern university. The neighbouring office houses Lee, a tenured but near-retirement professor who, until the bomb, is slowly drifting into career obscurity. Tired and solitary after two divorces, Lee suddenly finds himself in the public eye. This draws Lee to the attention of the bomber who reveals in a letter to Lee that he was once a colleague. Although not supplying his identity, events in Lee's early career at graduate school furnish an obvious candidate, and one that reopens unhealed wounds in Lee's life. His first marriage, to the now long-dead Aileen, was actually her second. An affair with Lee broke up Aileen's first marriage to the evangelical Christian Gaither, with the repercussion that Aileen never saw her son again. Lee's indifference to this lost son ultimately cost him his marriage to Aileen, the realisation of which gradually dawns on Lee as his thoughts return to Gaither after the bombing. However, embarrassed by these events in his life, Lee withholds the letter from the police and, now lost in reflections on his early life with Aileen, Lee becomes an increasingly isolated figure, suspiciously so to the authorities. Consequently, when Lee's failure to disclose the letter comes to light, they identify him as a "person of interest", a label that attracts the unwelcome attention of both the press and his suspicious neighbours. Forced by twitchy administrators into a leave of absence from his university, Lee is increasingly viewed, de facto, as the bomber, just waiting for his status to switch to "suspect". Backed into a corner in large part by his own actions, Lee decides to track down Gaither by himself, determined to unmask him as the bomber and to lay to rest his ghosts from the past. Secretly journeying to a remote countryside cabin, Lee discovers that his hatred of Gaither has blinded him, and that a different colleague from the same period as Gaither is actually the bomber. Fortunately for Lee, his efforts to evade the authorities have been amateurish, and they too close in on the cabin and apprehend the bomber. The novel closes with Lee now more clearly aware and understanding of the mistakes he has made in his life.
