Bombay, 1961. Sera Kotwal is told that her son will never grow, due to his brittle bones, but takes the news unexpectedly cheerfully. Her husband Sam and daughter Dolly meet the baby, and Dolly names him Brit.
Eight years later, Sam takes Brit to a holy man to be cured. Brit receives the Wagh Baba's blessing, but breaks a rib the next day after hiccupping. Sera puts on a record and encourages Brit to think of his birthday party, given by Sera's cousin Jeroo, whose deaf daughter Tina is Brit's great friend.
Sera takes her son to pay her husband a surprise visit at work, but Sam reacts with embarrassment.
The war with Pakistan sends family life into turmoil as Sera plans for their visits to the air raid shelters. Dolly reads that Wagh Baba has been exposed as a charlatan and a sex fiend, and Sam is mortified to find himself mentioned in the article. Brit overhears his parents arguing about the strain of looking after him.
After the war, Sam continues trying to make his son grow. A woman calling herself the Breathing Generator pays them a visit, claiming she can channel curative currents into the needy boy. Sam also concocts a rabbit jelly, made from the juice of goats' trotters, but Brit refuses to eat it.
Sera confides in her cousin Jeroo, who arranges a visit to Madame Maneckshaw. She entrances Brit, and takes over his education. Father Ferre, a Jesuit school head, allows Brit to take exams there while studying at home. Brit takes his work seriously, but is occasionally waylaid by growing sexual feelings. Despite this, at the end of the year he wins a prize - for being the bravest boy.
Jeroo plans to marry off Dolly, and broaches the subject cautiously with Sera. Their plotting is overheard by Brit, who reveals it to Dolly by pretending to talk in his sleep.
The next day they meet the suitor, Dinsu Dinshaw, and his mother Vera. While the women discuss financial arrangements, Dolly sets Dinsu a set of gruelling questions that she and Brit have prepared. Dinsu cannot answer any of them, so a delighted Dolly turns him down.
Sam tries to explain to Brit that it has been difficult for him to accept his disability, that he lacks Sera's resilience and optimism.
Madame Maneckshaw's husband dies, and Brit persuades Sera and Sam to take him to the funeral. When he sees the body laid out he is shocked to discover that it is Madame Maneckshaw, whose sister-in-law tells him about her suicide and gives him a letter.
Dolly tells a distraught Brit that she wants to marry Saleem, a doctor working in America. Sera cannot bear the thought of her daughter marrying a Muslim, but finally concedes. Sam agrees to accompany Dolly to America, where he kills himself by walking into a busy street blindfolded.
Five years later, new lodger Cyrus takes Brit to a disco and encourages him to dance, takes him swimming and plays the violin to him. Sera catches them kissing in Brit's bedroom.
Despite his misgivings, Brit is happy when Tina gets a boyfriend, Rohit, but then hears that she has disappeared. The couple is tracked down to a brothel, whose madam denies all knowledge of Tina - but Brit has a strong suspicion of what has happened. A grief-stricken Jeroo converts to Hinduism.
Cyrus has disappears for several weeks, reappearing to collect Brit to celebrate his birthday. Brit is initially thrilled but then devastated after he meets Amy, Cyrus' new girlfriend. When they return back to the flat, Brit examines his body in an attempt to understand Cyrus' betrayal.
Brit has an accident at the library, and is rescued by Amy, who accompanies him home, where they end up making love. Afterwards, they both jokingly confess that they wanted to understand what Cyrus has done. Sera is horrified to find a woman in the flat and throws Amy out.
The increasingly deranged Jeroo sprinkles holy water around Sera's flat. In the ensuing struggle, Sera is killed by an iron falling from the cupboard. After the funeral, Brit plays his parents' favourite tango and resolves to write his life story.
