Chess Hanrahan is the chief of police of Auberley, a university town in Massachusetts. He is a former New York City police detective who resigned after being blamed by a district attorney for the "unnecessary" death of a criminal in a gun fight. Auberley seemed to be a sanctuary from the politics and irrationality of the big city. Hanrahan admits to himself that he accepted the job in Auberley to lick his wounds. It was quiet, sedate, not much of a challenge.
But then a philosophy professor is murdered, and Hanaran can't understand why anyone would go to the trouble of murdering any college professor until he learns more about the man. The man was a war hero and the idol of David Perry, a graduate philosophy student, and was respected by others in Sloane University's department of philosophy faculty. But not by all.
As he delves into the possible motives for the murder, others are committed, including philosophy professors in other universities. The most curious one is of a fast food clerk who had no connection at all with Sloane.
He begins to grasp the rivalries between the professors and the reputations that are at stake between them and wealthy donors to the private school. Fraud, dishonesty, and the competition for donor dollars and a push for union representation of the philosophy professors enter the murderous equation.
Complicating the case is Hanrahan's distracting breakup with an old flame, and his interest in the murdered professor's former fiancé.
Another complication is the failure of David Perry, the murdered professor's star student, to pass his oral and written examinations. It is the consensus of the other faculty members that Perry ought to have passed the exams, and that another student, Mark Runge, ought to have failed his exams.
In the end, Hanrahan identifies the murderer - another faculty member - and closes the case having adopted a new motto, taken from one of Perry's test questions: "Nothing that is observable in reality is exempt from rational scrutiny." His personal issues resolved, and his confidence in himself restored, Hanrahan contemplates returning to New York City as a private detective.