The short story "My Son the Fanatic" centers around Punjabis who have immigrated to England. Parvez, the father, has adapted to the customs of his adopted country. He drives a taxi, drinks alcohol, watches Hollywood films, and befriends a prostitute. His son, Ali, has been studying to be an accountant and has also adapted well to English customs, but he abruptly experiences a change in his life.
The story does not go into the background of how it occurs, but somehow Ali has undergone a religious conversion. He has decided to become a devout Muslim and observe what he perceives as the regulations and strictures of the faith. This includes praying five times a day and abstaining from alcohol, pork meat, and other things. In some ways, this has a beneficial effect on Ali. He cleans up his room and attempts to behave in a moral manner.
However, this conversion also has a negative effect in that Ali becomes intensely self-righteous and judgmental of his father. Instead of being tolerant and manifesting acceptance of the opinions of others, he has become incisive and even cruel in condemning thoughts and ideas that are contrary to his own. This is why Parvez begins to consider his son a "fanatic" and also why Ali refuses to follow his father's advice. He not only observes strict religious practices but is completely intolerant of any other thoughts or ideas. He thinks that his father has been corrupted by Western civilization, and so he refuses to listen to him.