At the end of the book, love wins out over soullessness and hate; Meg matures and shows her competency; the Murry family is reunited; and Mrs. Whatsit, Who, and Which, their task completed, disappear.
This is a far cry from the book's beginning. At that point, Mr. Murry had disappeared, distressing his wife and children and causing gossip in the village. Meg, an adolescent, doesn't think she can do anything right as the novel opens—even her hair refuses to curl correctly.
With the help of Mrs. Whatsit, Who, and Which, Meg, Calvin, and Charles Wallace are able to tesser—or use wrinkles in time—to travel to Camazotz to rescue Mr. Murry. However, they have to leave behind Charles Wallace, whose mind has been possessed by IT. It is up to Meg to save him on a solo journey, which she successfully does by realizing her love for him is stronger than any other force.
By the end of the novel, Meg has matured. Rather than displaying incompetency, she succeeds at a daunting and adult task in saving her little brother. She learns to rely on herself rather than expecting her father to be her savior. As part of this feel-good ending, the family reunites:
Mr. Murry was running across the lawn, Mrs. Murry running toward him, and they were in each other’s arms, and then there was a tremendous happy jumble of arms and legs and hugging, the older Murrys and Meg and Charles Wallace and the twins, and Calvin grinning by them until Meg reached out and pulled him in and Mrs. Murry gave him a special hug all of his own.