Willie Dunne is born in Dublin, Ireland, in the winter of 1896. His happy and peaceful childhood is marred by his mother’s death in 1908 and his father’s disappointment that Willie won’t ever reach the six-foot height requirement to become a policemen. Unable to live up to the expectations of his father, who is chief superintendent of the Dublin Metropolitan Police, 16-year-old Willie becomes an apprentice to a builder named Dempsey. He works throughout the Dublin lockout of 1913, during which many employers refuse to hire laborers associated with trade unions. When Willie is almost 17, he meets Mr. Lawlor, who has lost his job as a carter because of the lockout. Mr. Lawlor tells Willie that every man should “[know] his own mind,” a lesson that stays with Willie for a long time. Willie also meets Mr. Lawlor’s daughter, Gretta, and he falls in love with her almost immediately.
In 1914, war breaks out in Europe, and Willie decides to join the Royal Dublin Fusiliers, an Irish regiment in the British Army. Willie does so mainly because he wants to please his father. He has no political motives for fighting in the war, unlike some Irish nationalists who believe joining the British Army will help Ireland achieve Home Rule, or Irish unionists who hope to block Home Rule. In fact, Willie knows little about the Home Rule conflict in Ireland, although he understands that his father dislikes nationalist politicians and believes firmly in “King and Country and Empire.”
Willie is also naïve and ignorant about the reality of war. He assumes that the war will end quickly, and that the fighting will be heroic. However, when Willie arrives at the Western Front in early 1915 and experiences trench warfare for the first time, he’s overwhelmed by fear and horror at the terrible violence he encounters. On the front lines, Willie befriends his fellow soldiers, Clancy and Williams, his sergeant-major Christy Moran, and his captain George Pasley. Their friendship helps sustain him through the hardships of war. Soon, however, the soldiers face a deadly gas attack near St. Julian. The poisonous gas creates terror and chaos, killing many of Willie’s comrades. Captain Pasley’s death in particular leaves Willie grief-stricken.
Later that winter, Willie’s company rests in Amiens, and Willie and Pete O’Hara visit a café. While they drink beer and dance with other soldiers, Willie mourns Captain Pasley and misses Gretta, whom he wants to marry. In January 1916, Willie sends an affectionate letter to Gretta. He wonders if he should tell her that he slept with a sex worker in Amiens, but he decides not to. Soon, Willie goes home on a brief leave from the Western Front. He reunites with his sisters, Maud, Annie, and Dolly, and his father, who tenderly bathes Willie. He also spends time with Gretta, who loves Willie but won’t marry him until after the war is over.
On the day that Willie is meant to return to the Western Front, he meets Jesse Kirwan in the soldiers’ barracks. Jesse is another member of the Royal Dublin Fusiliers and a supporter of John Redmond, an Irish nationalist leader. Before the soldiers can depart from Dublin, they’re ordered back into the city, where a battle is erupting between Irish rebels and British Army soldiers. Confused and troubled, Willie follows orders to engage with the insurgents. As he watches a young Irish rebel die, Willie wonders how he came to be fighting against his own countrymen.
In late April 1916, Willie rejoins his company in Belgium. The soldiers endure a second gas attack at Hulluch, where Willie kills a German soldier. After the battle, Willie and his comrades hear news about the aftermath of the recent insurrection in Dublin. The Irishmen feel conflicted about the failed uprising. On one hand, they blame the rebels for causing trouble at home. On the other hand, they regret that the rebel leaders are being executed. Willie writes a letter home to his father betraying his sympathy for the rebels.
Meanwhile, Father Buckley—the kind priest in Willie’s company—reveals to Willie that Jesse Kirwan is awaiting a court-martial for disobedience. When Willie speaks with Jesse in his holding cell, Jesse reveals that he can’t stand to serve obediently in the British Army now that the army is killing Irish nationalists. Willie tries to persuade him to repent so he can live, but Jesse refuses and is executed in August 1916. Willie helps bury Jesse’s body and sings the “Ave Maria” hymn at his grave.
That same night, O’Hara tells Willie a story about one of his earlier experiences in the war, during which he and a fellow soldier assaulted a Belgian woman. Horrified by this confession, Willie hits O’Hara. Later, Willie’s company marches through Guillemont and captures Guinchy successfully. However, the victory feels meaningless because so many men die in the battle.
During the winter of 1916, Willie’s company is in reserve, and the soldiers put on a boxing match, a play, and a dance for entertainment. At the end of this respite, Willie’s company returns to the front lines and fight in two battles. The first is the capture of Wytschaete in June 1917, after which Christy Moran earns a medal. The second is the battle at Langemark in August 1917, during which Father Buckley is killed.
That fall, Willie returns home on his second furlough. This time, Willie’s father is furious with him for sympathizing with the Irish rebels, and he accuses Willie of “villainy.” Frightened by his father’s anger, Willie leaves his family. He seeks out Gretta next, only to discover that she has married someone else because she learned from an anonymous letter that Willie was unfaithful to her while he was away. Willie apologizes, and Gretta wishes him well. Before Willie leaves Dublin, a group of boys taunts him by calling him a Tommie (slang for a British soldier) and telling him to go home.
Back on the Western Front, Willie turns 21 years old. In early spring of 1918, Willie and his comrades are caught in another bombardment. They retreat from their trenches and fight against German soldiers in the nearby woods. O’Hara is fatally wounded in the attack; before he dies, he admits to Willie that he sent the letter to Gretta revealing Willie’s infidelity. Then, a bomb explodes in the woods, severely injuring Willie.
Willie awakes in a military hospital in England, covered in burns and lacerations. After a few months, Willie recovers enough to return to the Western Front, although he feels weary, broken, and hopeless. All his suffering in the war has led him to conclude that humans are powerless against death. Moreover, Willie now understands that other Irishmen distrust him for being part of the British Army, while British soldiers distrust him for being Irish. Willie feels that he’s been abandoned by both his countrymen and the army. Nevertheless, in the summer of 1918, Willie rejoins his company, and the war continues on. Then, in October, Willie’s company prepares for a battle at St. Court. When Willie hears a German soldier singing “Silent Night,” he thinks about the meaninglessness of war and his own loneliness. Suddenly, Willie sings back to the German soldier, and he’s shot and killed. His friends bury him where he died before they must move on.