The core of the plot is the romantic triangle formed by the protagonist, a conscript soldier named Private Brigg, a worldly professional soldier named Sergeant Driscoll and Phillipa Raskin, the daughter of the Regimental Sergeant Major. The location is a British army base in Singapore during the Malayan Emergency.
Brigg and Phillipa are virgins in every sense of the word; they are both barely out of adolescence. Brigg is fearful of Phillipa's father and hardly dares go near her. He is equally afraid of the Malay and Chinese prostitutes in the nearby city. His only outlet is with his mates in the barracks, who fantasize endlessly about what they might do without actually knowing how to go ahead and do it.
Phillipa is getting more and more rebellious, eventually setting herself up with Sgt. Driscoll as a lover, while she leads Brigg on in the romance department. Brigg finally summons up the courage and the cash to approach a prostitute, called Juicy Lucy by the troops. The encounter starts disastrously but after Lucy realizes Brigg is a virgin, she takes pity on him and begins his education in her own way. This develops into a long-term relationship, at least for Brigg, who she calls affectionately "Bigg". Brigg tries not to think about what Lucy does when he is not with her.
Driscoll is seething with his own inner demons. He keeps taunting a Sgt. Wellbeloved with the phrase "Rusty nails!". Wellbeloved boasts constantly of keeping the Japanese busy during World War II, as a one-man guerilla army. Towards the end of the tale, the secret is revealed: Wellbeloved was a coward, and Rusty Nails was the nickname of the soldier he betrayed to the Japanese. Driscoll beats Wellbeloved to a pulp on behalf of the victim.
The novel crystallizes around violent incidents involving rioting in the city and an attack by Communist guerillas on a train. Several of Brigg's friends are killed. Brigg tries to find Lucy for solace, only to be told she was beaten to death by soldiers. (In the film, the locomotive destroyed was one of the last four used to haul mainline BR steam - the famous Fifteen Guinea Special.) Days before he is to be sent home, he confronts Phillipa with his frustrations, with unexpectedly pleasant results. For Phillipa, however, he is a passing fancy. Her sergeant awaits ...
Eventually Brigg and his remaining friends are about to embark for home. The final scene has them shouting the name of a laundryman, whom Brigg has mistakenly shot in the hand in an earlier episode, a certain Fuk Yew. It symbolizes their relation to Malaya and Malaya to them, when the tailor responds with the appropriate hand signal, using his damaged hand.
