The exposition of "A Wrinkle in Time" is at the very begininng, when the author introduces us to the characters: Meg, Charles Wallace, the mother, the twins, Mrs. Whatsit, Mrs. Who, Mrs. Which, and the father. The expositon as well as included the time, which was on a late, stormy 1960 night.
The father was sent on a mission in space and has not came back yet. He also stopped writing back to his family.
The characters meet the Mrs. Ws and Calvin and go off to space to find their father. They figure out the father is on the planet Camazots, so they tesser there.
IT takes over Charles Wallace's mind and so Meg, Calvin, and the father tesseract to a new planet.
There are friendly monsters on that planet that nurse Meg, Calvin, and Mr. Murry (the father) back to health.
Meg goes back to Camazots and gets Charles Wallace back to normal, using something IT doesn't have: the power of love. They all then tesser back to Earth and are welcomed home by their loved ones.