time and space with her younger brother Charles Wallace, her friend Calvin O'Keefe and three mystical beings called Mrs. Whatsit, Mrs. Who and Mrs. Which. They help them to rescue her father, a gifted scientist, from the evil forces that hold him prisoner on another planet. A Wind in the Door Meg, Calvin and the disagreeable school principal Mr. Jenkins have to travel inside one of Charles Wallace's mitochondria to save him from a deadly disease, part of a cosmic battle against the evil Echthroi and the forces of "Unnaming". A Swiftly Tilting Planet Charles Wallace must save the world from nuclear war by going back in time and changing might-have-beens, accompanied in spirit (through kything) by Meg at home. Many Waters Twins Dennys and Sandy accidentally play around with their father’s computer, sending them into Mr. Murry's experiment and back in time to the pre-flood days of Noah. They befriend his family, a group of seraphim, and some miniature mammoths. An Acceptable Time Meg and Calvin's eldest daughter, Polyhymnia O'Keefe, visits her maternal grandparents only to find herself trapped 3,000 years in the past, caught up in a struggle between the People of the Wind and the warlike, drought-stricken People Across the Lake. Setting The exact time period is never given, but the stories seem to take place in the 1960s and 70s. Since the series was written over the course of decades, it is not possible to establish an exact year in which each story takes place; historical events mentioned in the books (such as the dates of the Apollo space program and the name of the President of the United States) do not always correspond to the "real world". In recognition of this, and of the cosmic nature of the series, the inside front cover of Many Waters states that the series is set in Kairos, a way of looking at time as "real time, pure numbers with no measurement", reflecting her belief that "God's time and our time are not the same". Each of the books contains one or more instances of tessering, carrying the protagonists to metaphysical battlegrounds in the cosmic struggle between good and evil. The eponymous "wrinkle in time" is a short hop to the immediate past engineered by the Mrs. Ws to allow Meg, Calvin and Charles Wallace to accomplish their mission and return before they are missed at home. In A