The novel is about Will Freeman, a 36-year-old bachelor, and Marcus, an eccentric, introverted, bullied twelve-year-old who lives alone with his suicidal mother, Fiona. Will, who has never had to work thanks to the royalties from his father’s Christmas song hit entitled “Santa’s Super Sleigh”, has a lot of spare time. Most of this he spends smoking, watching TV, listening to albums and looking for female temporary companionship.
After a pleasant relationship with a single mother, Angie, Will comes up with the idea of attending a single parents group as a new way to pick up women. For this purpose, he invents a two-year-old son called Ned.
It is through one of these single parents meetings that he comes to know Marcus. Although their relationship is initially somewhat strained, they finally succeed in striking up a true friendship. Will helps Marcus to fit into the modern world. He takes him shopping, buys him shoes and introduces him to the music of Nirvana. Marcus and Will’s friendship blooms as the story progresses.
Marcus is “adopted” by Ellie McRae, a very tough fifteen-year-old girl, who is constantly in trouble at school because she insists on wearing a Kurt Cobain jumper. He also spends some time with his dad Clive, who visits Marcus and Fiona for Christmas, together with his new girlfriend Lindsey and Lindsey’s mother.
Meanwhile Will starts going out with a single mother called Rachel, whose son Alistair—“Ali” for short—is about the same age as Marcus. In the end, Marcus evolves into a “normal” child for his age. On the other hand, Will becomes more mature and ends up wanting to marry Rachel. Therefore, both Will and Marcus have started to live according to their age.