The jungles of Asia during WWII. Sergeant Mitchem is in charge of a seven-man patrol engaged on sonic warfare exercises to mislead the Japanese. He is fighting to regain his self-respect, following the loss of a stripe for losing a former patrol, while trying to ward off the naked disrespect of his second in command Corporal Johnstone. He is also plagued by the dour monotonous war-by-the-rules preaching of Lance Corporal Macleish, and above all, losing patience with the relentless tilting against authority of Private Bamforth, the 'barrackroom lawyer' of the patrol. The other three men, Privates Whitaker, Smith and Evans, have no particular axe to grind; they just want to return in one piece to their old lives back in civvy-street.
Bamforth delights in taunting the other men, drawing out their weaknesses and making them doubt the fidelity of their womenfolk back home. He hates the army and is always putting on funny voices, singing songs and generally 'performing' to his captive audience. Even the composition of the patrol is like a music hall joke - there is an Englishman, an Irishman, a Welshman, a Scotsman...
The patrol's first inkling that something is wrong comes from the radio. Whitaker has been trying vainly all day to get through to the main camp. Suddenly, the set crackles into life with the sound of Japanese. Mitchem decides they will try to get back to camp and tells his patrol not to panic - it is probably only a lone Japanese soldier. When Bamforth goes out to start packing the mules, he sees an enemy soldier scouting around. Hearing a noise, the man comes into the native hut where the patrol is hiding. He is captured by Johnstone who is all for killing him on the spot, until prevented by Mitchem, who decides they will take him back to camp with them.
Macleish and Smith are sent out to reconnoiter, and discover a Japanese scouting party nearby, in search of their missing comrade. Macleish and Smith manage to kill one of them, and escape. Back at the hut, Bamforth is set to guard the prisoner, who he nicknames Tojo. Despite the language barrier, Bamforth discovers that Tojo has a wife and family, and sees his photographs of them. Johnstone breaks up their 'conversation', still thirsting for the prisoner's blood. There is another radio message from the enemy, this time in English, letting the patrol know that they are coming! Mitchem decides it is useless to keep the prisoner alive, and resolves that he must be killed.
The patrol sets off, with Bamforth in charge of Tojo, through an old, disused mine, but find it flooded. They are forced to wait until the level of the water falls again. While Bamforth is posted on guard, the patrol's hostility to the prisoner is aroused once more when Johnstone discovers he is in possession of English cigarettes and assumes he has looted them from dead British soldiers. The prisoner is being brutally beaten up when Bamforth, summoned by his cries, explains that he gave Tojo the cigarettes. However, when an English cigarette case is found on the prisoner, even Bamforth's impassioned explanations are not enough to save him from the patrol's hatred.
Bamforth is now the only member of the group who opposes Tojo's death. The prisoner has inadvertently revealed an unexpected streak of compassion in him. But while Bamforth is striving desperately to avoid a cold-blooded killing, the enemy patrol is getting closer. At a crucial moment, the radio crackles into life with enemy voices. The prisoner, springing to his feet, begins to gesticulate and speak rapidly in Japanese, and Whitaker, in a panic, grabs a gun and shoots him.
The noise immediately gives away their position. Cornered, the patrol fights bravely but hopelessly. When the smoke clears, only Johnstone and Whitaker are left alive. They surrender.
Now the positions are reversed; the Japanese soldiers find Tojo's water bottle on Whitaker, and the cycle of suspicion starts all over again.
