A Wind in the Door is the sequel to A Wrinkle in Time, and finds Meg and her younger brother Charles Wallace embroiled in another cosmic adventure. This time, however, Charles Wallace is sick, and the two children have to journey into his mitochondria to meet the creatures who live there. They also team up with a dragon-like cherubim and Meg's unpleasant principal, Mr. Jenkins. The novel deals with the themes of space and time, love and evil, and the interconnectedness of the universe.
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