Father & Son tells the story of Luke Wright, a troubled 15-year-old boy who lives alone with his mother, Mallory — a part-time lap dancer — on a run-down housing estate in the heart of Bradford.
Luke, who is regularly in trouble at school, is suspended when he defends his friend and breaks a boy's nose. Mallory is furious with Luke and the school and threatens to report the headmaster to the authorities. Mallory disciplines Luke and grounds him for two weeks.
Luke rebels and sneaks out to visit a party with his best friend, Ashraf, putting further strain on Luke and Mallory's fractious relationship. And when Luke discovers a hidden letter from his estranged father, George, he finds his father is dying from a rare form of Leukaemia. Luke confronts Mallory, and they fight.
A distraught Luke turns to Mallory's ex-boyfriend, Michael, whom Luke admires and respects. Michael offers Luke a place to stay and agrees to mediate between Luke and his mother. But things deteriorate further when Mallory reveals she has hidden letters from Luke's dad for over ten years and lied about her affair with his father's brother.
Luke begs Michael to help him find his father. Michael agrees, buys Luke a ticket to London, and gives him some money. Luke sets off and makes friends on the train with a girl named Sky, who offers to help Luke find his father.
Luke and Sky spend all afternoon and evening looking for George without success. And when Luke reveals he doesn't have anywhere to stay for the night, Sky says he can stay with her and her friends. Luke agrees, and the two end up drinking and having sex. But when Luke wakes, he finds that Sky and her friends have left, robbing Luke of his money and mobile.
Luke is distraught and contacts Michael for help. Michael is furious with Luke but agrees to pick him up the following day. In the meantime, Luke will have to fend for himself and possibly sleep rough. Luke decides to continue his search. Luke is about to give up when he visits a pub popular with army veterans, where he bumps into his father's ex-girlfriend, Camilla.
Camilla tells Luke that his father has left London and gone to live by the seaside. Unfortunately, his father didn't say where and didn't leave a telephone number either. Camilla offers Luke a bed for the night, which he accepts.
The following morning, Michael, Mallory, and Ashraf take Luke home. On the journey back, Mallory thinks George may be staying in a seaside town they once visited on her honeymoon. They all agree and head to a North Yorkshire town called Saltburn.
They search all day for George without success. Thefamily are about to leave when Mallory sees a man resembling George walking along the pier. And when she discovers the man is Luke's father, Luke and George are reunited in a highly emotional scene, where George reveals he needs a bone marrow transplant.
Luke later discovers that his bone marrow is not a proper match for his father. Still, a mystery donor has come forward, and the operation is successful. Luke and Mallory then learn that the mystery donor is Michael.
The film ends several weeks later with Luke and his family celebrating Michael's birthday and George's good health at George's caravan, high above the cliffs of Saltburn-by-the-Sea.