The action of the novel begins in the year 2021 when the narrator decides to start writing into a journal. The first event noted into the journal is the death of a man named Joseph Ricardo, the last man to be born on earth. Theo, the narrator, is 50 years old and he is related to the man who ruled Britain, Xan Lyppiatt. Theo is a retired historian and his loneliness is what pushes him to want to write a diary.
The world in which Theo lives is a grim place, preparing to die and with no hope. The last man to be born was in 1995 and since then no births have been recorded. While the nations tries for years to find a cause for the mass infertility affecting the entire world, they were unsuccessful and soon the nations turned against one another, trying the be the first to discover a cure. When it became clear that the nations will not be able to find a cure in time, the population accepted their faith and instead of focusing on trying to find a cure, they focused on trying to make themselves as happy as possible. The population also dropped drastically as more and more people decided to kill themselves out of desperation. No children existed on earth and the population indulged in watching videos with children in the same manner a drug addict would enjoy using drugs.
The generation of children born in 1995 was considered as being special and thus the children became arrogant and unwilling to listen to anyone. Theo also mentioned that the generation became extremely violent, thinking that they were above the law since no one dared to stand up to them.
In the second chapter, Theo talks about his past and how he used to be his cousin’s advisor. Everyone believed the two to be close since they spent most of their time together but Theo claims that he could never understand his cousin. Xan never had any other friends over except Theo and Theo’s presence made Xan’s parents feel more relaxed, thinking that their son was having a normal social life. Theo used to spend his summers at his cousin’s house and he describes those moments as being the happiest moments in his life.
Theo remembers the first night he spent at Woolcombe, his cousin’s estate and how he was given a beautiful room to sleep in. Theo also thinks nostalgically that one day, the estate will end up deserted, with no one left alive to populate and live in the opulent castles and mansions of the world.
In the fourth chapter, Theo mentions his mother who was an artist. She made a living out of recreating paintings and selling them and sometimes Theo would help his mother by stealing prints and frames. Theo’s father died in 1983 from stomach cancer and Theo became the man of the house, a burden he was not keen to take on his shoulders.
In the fifth chapter, Theo mentions how in 1994, he accidentally killed his daughter Natalie when he run her over in the driveway. She was just 15 months old and after her death Theo and Helena’s relationship broke apart. Theo admitted that while he loved his daughter, he was not crushed by her death and he remained distant and cold. The couple moved from their old house into a new one but their relationship was never the same anymore. Theo reveals to the reader that his wife left him while also admitting that he used to cheat on her with his former students all the time.
Starting from the sixth chapter, the narrator changes and a third person begins narrating Theo’s life. Theo continued to teach at Oxford and to attend Church almost obsessively as a way of maintaining a routine. One day, while he left church, he was approached by a woman with a deformed hand. The woman in question was one of Theo’s former students and he agreed to talks with her. The woman’s name is Julian and she is the member of a small group trying to persuade the dictator of the country to act in the country’s best interest. Theo tells Julian that he has no power over Xan whatsoever but she insists that he must meet with her group.
Theo visits his former professor, a man named Jasper who chose to live in the countryside with his wife Hilda. The two chose to prepare for the end of the world by gathering large quantities of food and other things they deemed necessary. While Japer expressed his wish to move back to Oxford, his wife was depressed and told Theo that she plans to take part in a mass suicide with other elderly members. Theo is unwilling to let the couple live with him so he tries to suggest other ways of dealing with their depression.
That weekend, Theo goes to the Church to meet with Julian’s associates. Theo meets Julian’s husband, a man named Rolf and other members of the group. The group tells their demands to Theo who continues to try and convince them that he has no power whatsoever over his cousin. Theo also argues that no one will be interested in their demands since the general population does not care for change. Theo leaves but promises to talk with his cousin about the matters proposed by the group.
In the ninth chapter, Theo travels to Southwold to see a mass suicide called Quinetus. The old women are given white robs to dress into and they begin dancing to the music. The women are then given weights they tie to their legs and then are taken by boats away from the shore where they will be dropped into the ocean. Theo sees a woman trashing and fighting against the men trying to make her board the boat but when he tries to save her he is pushed aside by a police officer. That night, Theo stays at an inn and the next morning, when he tries to talk with the locals about the practice of mass suicide, they all deny its existence. After the event, Theo decides to help the group and to talk with his cousin about the situation in the country.
Theo then goes to see his cousin, a person he had not visited in many years. Theo is picked up by a driver sent by his cousin and on the road there Theo thinks about the members of the council and how they may react to his proposal.
Theo is taken into a room where the council members are waiting for him around a table. Theo presents his complains but the members refuse to listen to him, claiming that nothing they did was wrong. When Theo leaves, he feels as if he accomplished nothing at all.
When Theo leaves, Xan appears suddenly and takes him to a park where they can talk in private. Xan warns Theo that his power will not help Theo should he decide to push forward with his demands and that he misses the old times when they used to go to Woolcombe. The two depart and Xan warns Theo once more about the dangers of asking too many questions.
When Theo meets with Julian, he tells her about his conversation with Xan but Julian refuses to give up her dreams, claiming that she wants humanity to die in a dignified way and not be remembered as devils should another generation come after them. When Julian leaves, she lets Theo understand that she will not give up.
A few weeks later, Theo receives a pamphlet through he mail with the demands of the group who chose the name The Five Fishes. While Theo is moved by the words written in the pamphlet, he thinks that nothing can change so he destroys the pamphlet and throws it away.
Theo visits his former wife and her new lover. The two had a cat who gave birth to two kittens and the appearance of the little animals sparked a discussion about the regulations surrounding the breeding of animals and the pamphlet sent by the Five Fishes.
Theo is also visited by a member of the police who questions him about the pamphlets and about his involvement. Theo throws suspicion off him by claiming his loyalty towards his cousin is more important than anything. After they leave, Theo thinks of Julian and the rest of the group and wonders how he can help them or warn them about the danger they find themselves in.
Theo does meet with Julian one day at the market and he tries to warn her but she refuses to listen to him. After the encounter, Theo decided to leave and travel the world, hoping that in that way, he will find some kind of meaning.
In chapter 20, Theo returns to Oxford after an absence of six months. When he returns, he feels as if something is different and when he talks with Helena she tells him that things became tense in the country in the past few months. Theo worries about Julian and he tries searching for her at different churches but does not find her.
One night, a member of the group named Miriam shows on Theo’s doorstep and tells him that one of their own was taken by the police. Fearing that the man taken will reveal information about them, the group needs to leave the town as quick as possible. Miriam tries to convince Theo to help them, claiming that Julian needs him. Theo packs in a hurry and they leave the house quickly. Miriam also tells Theo that Julian is pregnant, something Theo does not believe only when he sees Julian and sees her belly. Theo insists that they must go and tell Xan about Julian’s pregnancy but Julian is afraid that the state will take the baby away from her. Theo tries to convince the group that the child belongs to mankind but the rest of the group claims that the child belongs to God and to his parents.
The group plans to find a safe house to stay until the baby is born and Theo is convinced to join them. The group decides to get as far away as possible from Oxford and change cars so it will be harder for the police to track them. Theo takes them to Jasper’s house where they find Jasper dead and they take his car and the food they find in his home. Theo also takes the gun with which Jasper killed himself before leaving the house behind and starting on their journey.
On the road, Theo and Rolf talks and Rolf expresses his desire to seize the power from Xan once the baby is born. He does not want however to change anything in the world and only wants the power. Theo points out that Xan will not let himself be overthrown and that he will most likely just kill Rolf and take what he wants from him.
After a few days of driving, the car is ambushed by a group of Omegas who begin attacking the car. Theo knows that the Omegas will kill one of them so he convinces Julian and Rolf to run while the others plan to stay behind and distract the Omegas. Everyone except Luke survives and unfortunately, the group’s supplies are also lost. The group recovers Luke’s body and Julian confesses that her child is fathered by Luke, not by her husband.
Theo, Miriam and Julian burry Luke’s body but Rolf decides to stay separate from them. The four sleep in the woods that night and the next morning they find that Rolf left the group. Instead of letting themselves be consumed by despair, Theo decides that they must continue with their plan and that he will try and find a car for them.
Theo goes into the nearest village where he steals a car and supplies from an elderly couple. Theo leaves the couple unharmed and then runs away with their car, thinking about Julian and her baby and how in other parts of the world, other children may also be conceived and born.
When Theo returns to camp, Miriam tells him that Julian went into labor so Theo decides to return to a place he deemed as being safe for Julian to give birth. When Theo turns on the radio, he hears that their small group is wanted by the government and that the elderly couple he stole from died in the middle of the night.
The group reaches the small cottage and Theo goes for a walk as Julian enters the final stages of labor. When he returns, he makes a fire and stays by Julian’s side as she gives birth to a baby boy. Theo goes looking for Miriam who went out looking for water and he soon finds her dead. Knowing that their group was discovered, Theo returns to the hut and tells Julian what he has found.
Soon after, Xan also appears but does not know that the baby was born. He tries to assure Theo that nothing will happen to him for the baby and his mother but Theo has a hard time believing his words. Theo kills Xan and takes his ring, ensuring that he will be the next ruler of England. The members of the council emerge from the woods and they are allowed to see the newborn baby.
When Julian sees the ring, she understands that Theo killed Xan and asks him to christen her child. The novel ends with Theo, kneeling beside Julian, making the sign of the cross on the baby’s forehead.
