She tells her sister Cassandra that she wants to live in a Jane Austen novel. Rose, Mortmain's elder daughter, is a classic English beauty pining away in the lonely castle, longing for a chance to meet eligible and preferably rich young men. The widowed Mortmain's second wife, Topaz, is a beautiful artist's model who enjoys communing with nature, sometimes wearing nothing but hip boots. Now his family is selling off the furniture to buy food. Ten years before the novel begins he took out a forty-year lease on a dilapidated but beautiful castle, hoping to find either inspiration or isolation there. Cassandra's father is a writer suffering from writer's block who has not published anything since his first book, Jacob Wrestling (a reference to Jacob wrestling with the angel), an innovative and 'difficult' modernist novel that sold well and made his name, including in the United States. The Mortmain family is genteel, poor, and eccentric. The novel takes place between April and October in a single year in the 1930s. In 2003 the novel was listed at number 82 in the BBC's survey The Big Read. It is a coming-of-age story in which Cassandra passes from being a girl at the beginning to being a young woman at the end. The first person narrator is Cassandra Mortmain, an intelligent teenager who tells the story through her journal. The novel relates the adventures of an eccentric family, the Mortmains, struggling to live in genteel poverty in a decaying castle during the 1930s.

Smith was already an established playwright and later became famous for writing the children's classic The Hundred and One Dalmatians. She longed for home and wrote of a happier time, unspecified in the novel apart from a reference to living in the 1930s.

I Capture the Castle is the first novel by the English author Dodie Smith, written during the Second World War when she and her husband Alec Beesley (also English and a conscientious objector) had relocated to California.

I capture the castle pages