In the British trenches before Saint-Quentin, Captain Hardy converses with Lieutenant Osborne, an older man and public school master, who has come to relieve him. Hardy jokes about the behaviour of Captain Stanhope, who has turned to alcohol to cope with the stress which the war has caused him. While Hardy jokes, Osborne defends Stanhope and describes him as "the best company commander we've got".
Private Mason, a servant cook, often forgets about ingredients and key parts of the food that he prepares for the officers.
Second Lieutenant Trotter is a rotund officer commissioned from the ranks who likes his food; he can't stand the war and counts down each hour that he serves in the front line by drawing circles onto a piece of paper and then colouring them in.
Second Lieutenant James "Jimmy" Raleigh is a young and naive officer who joins the company. Raleigh knew Stanhope from school, where Stanhope was skipper at rugby; Raleigh refers to Stanhope as Dennis.
Raleigh admits that he requested to be sent to Stanhope's company. Osborne hints to Raleigh that Stanhope will not be the same person he knew from school, as the experiences of war have changed him; however, Raleigh does not seem to understand.
Stanhope is angry that Raleigh has been allowed to join him and describes the boy as a hero-worshipper. As Stanhope is in a relationship with Raleigh's sister Madge, he is concerned that Raleigh will write home and inform his sister of Stanhope's drinking. Stanhope tells Osborne that he will censor Raleigh's letters so this will not happen; Osborne does not approve.
Stanhope has a keen sense of duty and feels that he must continue to serve rather than take leave to which he is entitled. He criticises another soldier, Second Lieutenant Hibbert, who he thinks is faking neuralgia in the eye so that he can be sent home instead of continuing fighting.
Osborne puts a tired and somewhat drunk Stanhope to bed. Stanhope (and the other officers) refer to Osborne as "Uncle".
Trotter and Mason converse about the bacon rashers which the company has to eat. Trotter talks about how the start of spring makes him feel youthful; he also talks about the hollyhocks which he has planted. These conversations are a way of escaping the trenches and the reality of the war.
Osborne and Raleigh discuss how slowly time passes at the front, and the fact that both of them played rugby before the war and that Osborne was a schoolmaster before he signed up to fight. While Raleigh appears interested, Osborne points out that it is of little use now.
Osborne describes the madness of war when describing how German soldiers allowed the British to rescue a wounded soldier in No Man's Land, while the next day the two sides shelled each other heavily. He describes the war as "silly".
Stanhope announces that the barbed wire around the trenches needs to be mended. Information gathered from a captured German indicates that an enemy attack is planned to begin on Thursday morning, only two days away.
Stanhope confiscates a letter from Raleigh, insisting on his right to censor it. Stanhope is in a relationship with Raleigh's sister and is worried that, in the letter, Raleigh will reveal Stanhope's growing alcoholism. Full of self-loathing, Stanhope accedes to Osborne's offer to read the letter for him. The letter is, in fact, full of praise for Stanhope. The scene ends with Stanhope quietly demurring from Osborne's suggestion to re-seal the envelope.
In a meeting with the Sergeant Major it is announced that the attack is taking place on Thursday. Stanhope and the Sergeant-Major discuss battle plans. The Colonel relays orders that the General wants a raid to take place on the German trench prior to the attack, "a surprise daylight raid", all previous raids having been made under cover of darkness, and that they want to be informed of the outcome by 7 p.m. Stanhope states that such a plan is absurd, and that the General and his staff merely want this so their dinner will not be delayed.
The Colonel agrees with Stanhope but says that orders are orders, and they must be obeyed. Later, it is stated that in a similar raid, after the British artillery bombardment, the Germans had tied red rag to the gaps in the barbed wire so that their soldiers knew exactly where to train their machine guns.
It is decided that Osborne and Raleigh will be the officers to go on the raid, despite the fact that Raleigh has only recently entered the war.
Hibbert complains to Stanhope about the neuralgia he states he has been suffering from. Stanhope replies: "it would be better to die from the pain, than from being shot for desertion". Hibbert maintains that he does have neuralgia and the right to leave the battlefield to seek treatment, but when Stanhope threatens to shoot him if he goes, Hibbert breaks down crying. He says "Go on then, shoot!", suggesting that he would rather die than stay on the battlefield. The two soldiers admit to each other that they feel exactly the same way, and are struggling to cope with the stresses that the war is putting on them. Stanhope comforts Hibbert by saying they can go on duty together.
Osborne reads aloud to Trotter from Lewis Carroll's Alice's Adventures in Wonderland; another attempt to escape from the realities of the war. The scene ends with the idealistic Raleigh, who is untouched by the war, stating that it is "frightfully exciting" that he has been picked for the raid.
There is confirmation that the raid is still going ahead. The Colonel states that a German soldier needs to be captured so that intelligence can be extracted from him. Osborne admits to Stanhope that he knows he's probably not coming back, and asks Stanhope to look after his most cherished possessions and send them to his wife if he does not return after the raid. In the minutes before going over the top, Raleigh and Osborne talk about home – the New Forest and the town of Lyndhurst – to pass the time. Smoke-bombs are fired, the soldiers move towards the German trench, and a young German soldier is captured. However, Stanhope finds out that Osborne has been killed although Raleigh has survived.
Stanhope sarcastically states, "How awfully nice – if the Brigadier's pleased", when the Colonel's first concern is whether information has been gathered, not whether all the soldiers have returned safely. Six of ten other ranks have been killed.
Trotter, Stanhope, and Hibbert drink and talk about women. They all appear to be enjoying themselves until Hibbert is annoyed when Stanhope tells him to go to bed, and he tells Stanhope to go to bed instead, then Stanhope suddenly becomes angry and begins to shout at Hibbert, and tells him to clear off and get out.
Stanhope also becomes angry at Raleigh, who did not eat with the officers that night but preferred to eat with his men. Stanhope is offended by this, and Raleigh eventually admits that he feels he cannot eat while he thinks that Osborne is dead, and his body is in No Man's Land. Stanhope is angry because Raleigh had seemed to imply that Stanhope didn't care about Osborne's death because Stanhope was eating and drinking. Stanhope yells at Raleigh that he drinks to cope with the fact that Osborne died, to forget. Stanhope asks to be left alone and angrily tells Raleigh to leave.
The German attack on the British trenches approaches, and the Sergeant Major tells Stanhope they should expect heavy losses. When it arrives, Hibbert is reluctant to get out of bed and into the trenches.
A message is relayed to Stanhope telling him that Raleigh has been injured by a shell and that his spine is damaged, meaning he can't move his legs. Stanhope orders that Raleigh be brought into his dugout. He comforts Raleigh while Raleigh lies in bed. Raleigh says that he is cold and that it is becoming dark; Stanhope moves the candle to the bed and goes deeper into the dugout to fetch a blanket, but, by the time he returns, Raleigh has died.
The shells continue to explode in the background. Stanhope receives a message that he is needed. He gets up to leave and, after he has exited, a mortar hits the dugout causing it to collapse and entomb Raleigh's corpse.