A Wind in the Door is a fantasy novel in the Time Quintet series by Madeleine L'Engle. It was published on January 1st, 1973, by Farrar, Straus, and Giroux. It is a companion book to L'Engle's 1963 novel, A Wrinkle in Time. It is followed by its sequel, A Swiftly Tilting Planet.
The novel includes the same characters as A Wrinkle in Time, though it is not a sequel. It began as a short story titled Intergalactic P.S. 3. It was published as a pamphlet in 1970. During the following three years, the concept expanded into a 240-page novel.
One of the significant themes in the novel is the concept of the power of the individual. The main character Meg Murry, who is portrayed as an average teenager, is able to save her brother Charles Wallace through her own strength and determination. The novel encourages readers to believe in their own abilities and to have confidence in themselves.
A Wind in the Door received mostly positive reviews upon release. It was praised in The School Library Journal as "complex and rich" and a "breathtaking environment." In 1978, it received the Learning A-V Award.