Private Peaceful follows the early life of Tommo Peaceful, and is told from his perspective. The novel alternates back and forth between the present and Tommo’s recollections of the past.
The narrative begins in Tommo’s childhood. He is nervous about his first day of school, but his brother Charlie reassures him and gives him a piggyback on the way. Tommo is dreading school, but once he has arrived he meets a girl named Molly, who helps him to tie his shoelaces and smiles at him. Tommo knows from this first day that Molly will become his friend.
Tommo has a flashback to a day in the woods with his father. Tommo’s father was a woodcutter, and Tommo had joined him for the day. Tommo went off to play in the woods, and became engrossed in his imaginary games. Suddenly he heard a noise, and realized that a tree was falling. If he didn’t move, it would fall right on top of him, but he found himself frozen with fear. Before he knew it, his father was shouting and running at him. Tommo survived, but his father was crushed by the tree.
Tommo attends his father’s funeral in the village church with his family. They all notice a swallow swooping around the church, and Tommo thinks that the swallow is the spirit of his father trying to escape. After the funeral, Tommo’s mother tells Big Joe (Tommo and Charlie’s brother) that their father is up in heaven and “happy as the birds.” Tommo, however, feels burdened by the terrible guilt that he is responsible for his father’s death.
Big Joe has had brain damage since birth, which means that he is slightly “different” to his brothers, but they love him regardless. To them, he is just “Big Joe,” and he is always completely trusting, happy, smiling, and kind. One day, Molly tells Tommo that she likes Big Joe because she thinks he is kind, and Tommo decides that he will love her forever. Molly soon practically becomes part of the Peaceful family. She comes home with the boys every day after school, and the three kids become almost inseparable.
Everything is relatively happy in Tommo’s life for a while. The only problem is that he feels left out of his friendship with Molly and Charlie, because they are older than him. They both leave school and start work up at the village estate, which is owned by a terrible man named the Colonel, but Tommo is left behind in class. One day he sees Molly and Charlie holding hands, and feels a deep pang of “loss” and sadness. He realizes that they are leaving him behind and falling in love with each other.
Charlie has started a job working at the hunt kennels at the estate. One day, he confesses to Tommo that he’s in deep trouble. He has rescued a dog from the kennels because it was going to be shot, but he knows that the Colonel will accuse him of stealing it. Sure enough, the Colonel fires Charlie the next morning, and later kills Bertha the dog anyway, just out of personal spite.
After the dog incident, the Colonel tells Molly’s mother and Molly’s father that Charlie is a bad influence, so they ban Molly from seeing Charlie. Nevertheless, Charlie and Molly continue to meet each other in secret. Weeks later, Molly becomes accidentally pregnant, and is kicked out by her parents. Luckily, the Peaceful family welcome her with open arms, and Charlie promises to look after her and their baby. They get married soon after, although no one but the Peacefuls comes to the wedding.
Soon afterwards, the Colonel makes up his mind that Charlie must enlist to fight in the war, and tells the Peacefuls that he will evict them from their cottage (which the Colonel owns) if Charlie refuses. Charlie bravely accepts his fate, and Tommo resolves to join him, as Tommo is technically too young to be fighting anyway (he is only fifteen).
When the boys arrive at their training camp in France, they meet a terrible man named Sergeant Hanley. The arrogant Hanley is in charge of their company, and takes an instant dislike to Charlie, because Charlie won’t submit to him as the other men do. Hanley even starts picking on Tommo purely because he is Charlie’s brother. One day, Tommo becomes so exhausted from Hanley’s punishments that he collapses, and Charlie is so angry that he screams at Hanley in front of everyone. Hanley punishes Charlie, but the courageous Charlie takes his punishment with characteristic dignity.
Soon the soldiers are sent up to the front line, but find it to be very quiet at first. Their morale is kept high by Captain Wilkes, who often encourages the men to sing to stay jolly. Charlie and Tommo get everyone singing “Oranges and Lemons,” because it is a song that Big Joe always used to sing at home. The trenches are cold and full of rats and lice, but there is little fighting at first. The soldiers particularly enjoy visits to a local pub, where Tommo takes a liking to one of the waitresses.
One day, the company captures a German prisoner during an attack. The British soldiers realize that the German is actually just like them: he prays to the same God, and he looks exactly the same as them without his uniform on. They even share a cup of tea before he is taken away. Captain Wilkes is injured in the same mission that captures the German prisoner. Charlie loyally carries him to safety, and as thanks for his bravery and loyalty, Wilkes later leaves his precious golden watch to Charlie.
The company are sent up to the front line again. Their new commander is a man named Lieutenant Buckland, who has come straight from England. The soldiers think he seems young and inexperienced because of this, as he has seen less of the war than they have. One day, the British men head into battle, and Tommo is gravely injured. He can’t move his legs, and he loses sight of Charlie in the chaos. Lieutenant Buckland proves his naysayers wrong and courageously comes to Tommo’s assistance. He tries to carry Tommo back to safety, but is tragically killed as he stands by Tommo’s side.
When Tommo finally gets back to the trenches, he can’t find Charlie, and assumes that he is dead. In the middle of the night, Charlie returns. He was injured and couldn’t get back before now. The brothers hug each other and cry tears of relief. Charlie is taken to hospital, and when Tommo goes to visit him he learns that Charlie is being sent back to England to recover, which Tommo is very bitter about. Charlie manages to visit home while he is recovering in England, and meets his baby son for the first time. The baby has been called Thomas, or Little Tommo, in honor of Tommo.
Tommo decides to be brave and ask the girl in the local pub for her name. She tells him it is Anna, and they start to talk a little over his next few visits. One day, Tommo arrives at the pub and cannot see Anna anywhere. He tries to find her at her house, but Anna’s father tells Tommo that she has been killed by a stray explosion. Tommo goes to visit her grave and then returns despondently to camp. He wants to believe that Anna is in heaven, but finds that his faith has been destroyed by the war.
The next commander of Tommo’s company is none other than Sergeant “Horrible” Hanley, who proceeds to make all of the soldiers’ lives a living hell, constantly punishing them for the tiniest of offences. He becomes even worse when Charlie returns, and tells Charlie that he will be keeping a close eye on him.
In a huge battle a few weeks later, Tommo is gravely injured again. He feels a burning pain in his head and loses consciousness, and thinks that he is dying. Charlie pulls him up, and Tommo miraculously survives. The whole company are sheltering in a dugout, because they are surrounded on all sides by German guns. Everyone agrees that they should stay put, as to leave the dugout would be a case of almost certain death. Sergeant Hanley, however, has other ideas, and orders the men to move out and attack. Charlie refuses, telling him that this is a suicidal and pointless order, and that he will not abandon Tommo. Hanley tells Charlie that he will be executed if he doesn’t obey his order, but Charlie stubbornly stays put. The men go out to fight, and Charlie and Tommo remain in the dugout. While they wait, Charlie asks Tommo to promise that he will look after Molly and Little Tommo should anything happen to him, and Tommo agrees.
Only a few men return from the attack, unfortunately with Hanley still in their midst. As soon as they reach the British trenches again, Charlie is taken away under arrest. Six weeks later, Tommo is allowed to visit Charlie. It has already been decided that Charlie is going to be executed “for cowardice.” He will be executed tomorrow, and Tommo is only allowed to visit him for twenty minutes today. Charlie tells Tommo about his trial, which was completely unfair. He wasn’t allowed any witnesses, as the only possible witness was Tommo, who, as his brother, was deemed too biased. The only other person present was Sergeant Hanley. The judges listed to everything Hanley had to say and then blatantly ignored Charlie. They were biased from the start of the trial, and the verdict was made in less than an hour.
The boys then spend their remaining time together talking about their home. They end Tommo’s visit by singing “Oranges and Lemons” together, and then Tommo is called away. Tommo waits in a barn overnight for Charlie’s execution the next morning. His fellow soldiers try to offer him support, but he turns them all away and decides to spend the night alone, reflecting back on his past and his memories of Charlie. This is the story that the reader has just read.
When the time of Charlie’s execution arrives, Tommo goes outside and sings “Oranges and Lemons.” He knows Charlie will be singing it too, and it helps Tommo to feel connected to Charlie in his final moments. Tommo is sure that Charlie will be facing his death with dignity, with his head held high and a smile on his face. When he returns to camp, he finds all of his fellow soldiers standing to attention outside their tents to honor Charlie’s passing. The next day, Tommo’s regiment leaves for the Somme. All Tommo can think now is that he “must survive.” He has “promises to keep.”