Marcus is a 12-year-old boy who moves to London with his mother, Fiona, after she splits up with Marcus’ father. Fiona suffers from depression and Marcus worries about her. He also worries about starting a new school. Will Freeman is a 36-year-old man who lives in London and has never worked because he lives off the royalties of a Christmas song his father wrote years ago. He has lots of girlfriends but never gets serious because he hates the idea of being settled with a family.
Will joins SPAT (Single Parents Alone Together) because he thinks that if he goes out with single mothers he will have all the benefits of a family but none of the drawbacks. He invents a child called Ned, and talks about him to Suzie, a single mother at the group. She invites him to go with her on an outing with the group, and he meets Marcus, who is brought along by Suzie. Marcus accidentally kills a duck and Will protects him from the park keeper.
When Suzie and Will take Marcus home, they find Fiona unconscious in her flat after she has taken an overdose. They call an ambulance and her stomach is pumped. Marcus stays with Suzie until his mother is allowed home. He feels very worried and scared all the time. At school he is being bullied but he has nobody he can talk to.
Marcus follows Will and finds out that he has no child. He threatens to tell the SPAT members and begins to visit him after school. They develop a routine of watching TV together. Will buys Marcus some new trainers but they are stolen by school bullies. When Marcus is called to see the headmistress about the theft, he meets a girl called Ellie, whom he adores as she protects him from the bullies. Ellie loves Kurt Cobain, the lead singer of Nirvana.
Will is invited to spend Christmas with Marcus and Fiona. He is not looking forward to it and accepts reluctantly, but finds that he quite enjoys himself at first. However, by the end, when Fiona and Marcus start singing earnestly, with no sense of humour, he tells himself that he does not care if he never sees them again.
Will falls in love with a single mother called Rachel. He pretends that Marcus is his son and takes him to meet her son Ali, who is also 12 years old, and who threatens to kill Marcus if his mother goes out with Will. Marcus runs away but Will goes after him and tells him that Ali was crying, which cheers Marcus up. Rachel finds out that Marcus is not Will’s son, but forgives him. She likes the way that he cares about Marcus.
Will tells Rachel that he would like her to meet Fiona as she could talk to her about her depression. They arrange to meet in a pub but Rachel does not turn up. Will is forced to have a serious conversation with Fiona and he realises that Rachel set him up so that he would have to deal with it himself. He has never faced up to problems before and he finds that he enjoys it.
Clive, Marcus’ father, breaks his collar bone and wants Marcus to visit him and his girlfriend Lindsey in Cambridge. Ellie goes with him but it is the day that Kurt Cobain shoots himself so she gets drunk on the train. She breaks the window of a music shop and steals a cardboard cut-out of Cobain. Marcus decides that Ellie is too much for him. They are taken to the police station and Clive, Lindsey, Will, Fiona and Ellie’s mother, Katrina, all turn up to collect them. Will realises that he actually likes being a part of this large group of inter-connected people. He settles into a life with Rachel and Ali, and still sees Marcus regularly.