After a bath, Father dries Christopher off and puts him in bed. Father apologizes for lying about Mother and keeping the letters from Christopher. He doesn’t want any more lies between them, so he confesses to killing Wellington. He explains how upset he was when Mother left him. Mrs. Shears helped him to get through it, but when he recently had an argument with Mrs. Shears, Mrs. Shears kicked him out of her house, and Wellington attacked him in the yard. Father killed Wellington with the garden fork. Christopher screams in terror at the news, and pushes Father off the bed. Father retreats downstairs, begging Christopher to go to sleep so that they can talk about the situation in the morning. Christopher decides he can’t trust Father. Because Father murdered Wellington, Christopher reasons, Father could also murder him. Christopher waits until 1:20 a.m., takes out his Swiss Army knife, and walks quietly downstairs. In the living room, Father sleeps on the sofa. Christopher goes into the kitchen, takes his special food box, and steps out into the garden. He hides behind the garden shed and eats two clementines and a Milkybar, then wonders what to do next.
From the space behind the shed, Christopher can see the constellation Orion. He says people call it Orion because it looks like a hunter with a club, but he says the stars in the constellation can be joined to make any number of shapes, such as a dinosaur. At any rate, he says, Orion is not a hunter: it is a series of 21 stars billions of miles away.
Christopher sleeps in the garden that night. In the morning, he hides as he hears Father come outside looking for him. After Father leaves, Christopher decides he should live with Mrs. Shears, but when he knocks on her door she doesn’t answer. He goes through the reasons he can’t live with Siobhan, Uncle Terry, or Mrs. Alexander, then decides to go to London to find Mother. The prospect frightens him because he has never been anywhere on his own before, but the idea of returning to Father’s house, or hiding in the garden every night, is far worse.
Christopher notices the circular lid of an old metal pan leaning against the side of Mrs. Shears’s house. The pan looks like the surface of a planet, with rust forming continents and islands. The image reminds him of his dream to become an astronaut, and he feels disappointed at how impossible it now seems. Going to London, which is only a hundred miles away, scares him. He would have to travel thousands of miles away as an astronaut.
Christopher goes to Mrs. Alexander’s house and tells her he needs someone to watch Toby while he goes to London. He says he is going to live with Mother because Father lied to him about Mother’s death and killed Wellington. Mrs. Alexander tries to get him to come inside, but when she says she’s going to phone Father, Christopher panics and runs back home. Christopher grabs his schoolbag and fills it with food, a change of clothes, and some math books. He feels afraid when he spots Father’s mobile phone and wallet next to the kitchen sink, but remembering that Father’s van was not outside, he realizes Father forgot the items. Christopher takes Father’s bankcard, the pin to which Father told Christopher in case Christopher ever needed it.
Christopher puts Toby in his pocket and walks to school, intending to ask Siobhan the location of the train station. The further Christopher gets from home the less frightened he feels of Father but the more frightened he feels of being alone. He describes his fear as mathematically constant.