As the new school year starts in September, Roy Straitley is looking forward to his 100th term at St Oswald’s, where he has been teaching for 33 years. Having never married, he lives alone and has devoted his life to his career. His sitting room walls are full of pictures of “his boys”, and St Oswald’s represents his only family. He is slightly overweight and ugly by conventional standards (his nickname among his pupils is “Quaz”, short for “Quasimodo“). Popular with the students, he adheres to the old principle of being “firm but fair” where teaching and disciplinary matters are concerned. An incurable optimist, Straitley is only uncomfortable when he has to deal with the opposite sex. He is a keen observer, and hardly anything connected with life at the school, however insignificant, ever escapes his notice. A firm believer in the advantages and importance of a classical education, he shuns computers, resorts to Latin to swear and insult his colleagues (which they do not understand), and opposes the idea of any competition between schools other than the kind which is carried out on the playing fieldsSmoking Gauloises in his empty form room is his “one concession to the influence of the Modern Languages”, and there is long-standing enmity between Straitley and Dr Devine, the Head of German.

The other masters are mostly set in their ways, St Oswald’s having made an indelible imprint on their lives. There is Pat Bishop, the Second Master, who has also remained unmarried and who occasionally, at busy times, spends the night in his office doing administrative work. Always intent on mediating between rivalling factions, Bishop has been able to keep his affair with his secretary a secret so as not to blemish the school’s reputation. There is Bob Strange, the Third Master, a bureaucrat unpopular with the pupils who has been trying for years to get rid of Straitley and force him into early retirement (“Young blood is cheaper.”). There are the members of the German department (“Teutons“, according to the old Latin master), among them Geoff and Penny (“League of”) Nations, a married couple described by Straitley as hypocrites and sycophants. There is Tony Beard, head of computer science and eo ipso Straitley’s natural adversary. And there is Isabelle Tapi, a part-time French teacher who is said to have made passes at each new male addition to the staff.

At the beginning of the new term, it is the “freshers” on whom Straitley focuses his observations. There are five of them, among them Jeff Light, a Games master who has become a teacher because he thinks it is an easy job; Chris Keane, who teaches English but actually wants to be a novelist; and Dianne Dare, an attractive young woman who teaches French.

The new term starts with a number of minor yet inexplicable occurrences. For the first time in his life, Straitley’s register goes missing without ever turning up again. Also, his coffee mug is no longer at the place in the Common Room where it has sat for many years. Pupils report that various objects are missing from their classrooms or lockers. In particular, a 13-year-old Jewish boy from Straitley’s form deplores the alleged theft of his expensive fountain pen, a Bar Mitzvah present. Presently, the boy’s mother accuses the school and especially Straitley of anti-Semitism. Soon afterwards, a pupil in Straitley’s class nearly dies, following another malicious trick, and closely guarded secrets in the lives of the St Oswald’s staff are anonymously revealed. Life at St Oswald’s begins to suffer a gradual disintegration. One morning, after the discovery of a computer virus on the school’s computer system, Pat Bishop is arrested, because child pornography has been downloaded onto his computer and paid for with his credit card. Bishop denies this, but the damage to his career has been done. Meanwhile, a mysterious figure called “Mole” publishes in the local newspaper damaging allegations about St Oswald’s.

Straitley begins to suspect that, not only are all these incidents orchestrated by the same malicious individual, but that this person is deliberately trying to bring down St. Oswald’s.

The novel is written using Harris’ typical split-narrative technique. The first narrator (indicated at the beginning of each chapter by a white King) is Straitley himself, and focuses on the day-to-day events at St Oswald’s as the situation develops. The second is marked by a Black Pawn, and is the voice of the mysterious enemy within St Oswald’s, whose identity is only revealed at the end of the book, and who, little by little, reveals the bitterness and hatred that drives a person to fake an identity, break the law and even to commit murder – all in the name of revenge.