As in previous times when they've appeared, Mrs. Whatsit, Mrs. Who, and Mrs. Which cannot fully materialize on the beasts' planet. Meg begins complaining to them about her father, but they, who clearly have a lot of respect for Meg's father, will have none of it. Mr. Murry tells them that he is going to try to return to Camazotz to get Charles back, but Mrs. Which tells him that were he to go he would not be successful. Calvin then offers to go, since he almost got through to Charles those few times, but Mrs. Whatsit forbids it, saying that he would have to go so deep into IT to save Charles that Calvin himself would be lost. A silence follows.
In this scene, the respect and love that the Mrs. W's show to Mr. Murry and Calvin in not letting them go to Camazotz and that Mr. Murry and Calvin show for Charles by offering to go by themselves is admirable…only Meg hasn't show this spirit of self-sacrifice coming from love yet.
Meg realizes that she is the one who must rescue Charles. She feels terrified and overwhelmed, bursts into tears, and cries out, "All right, I'll go, I know you want me to go!" To which Mrs. Whatsit sternly replies, "We want nothing from you that you do without grace, or that you do without understanding." And with that sentence, Meg's resentment leaves her. She forgives her father in her heart, and then clearly explains to all of them that she understands it must be her, because she out of all of them knows and loves Charles best.
One of the most important points of the book is that acts of love must be freely given: Meg's going to Camazotz is worthless unless she chooses to do it of her own free will. She matures when she sees that only she can save Charles, and when she chooses to put herself in grave danger out of love for him, not out of a sense of coercion from the Mrs. W's. To act from coercion, without understanding, would be a kind of conformity.
Mr. Murry and Calvin immediately protest Meg going back to Camazotz alone. But they are persuaded when Mrs. Whatsit tells them that she and the Happy Medium have both seen that for Meg to go alone is the only way Charles may be saved, though they don't know what will happen…but they do believe she will succeed, because it is her fate. When Calvin asks if they know what's going to happen, Mrs. Whatsit tells him they don't, because that would be living like the people on Camazotz, with their lives all planned out for them. She explains to a confused Calvin that fate and freedom are compatible, just like a poet is constrained by a certain rhyme and meter in a sonnet but can say whatever he likes in the lines.
There is a sense of Divine Providence in the events of this novel; Mrs. Whatsit and the Medium somehow know ahead of time what will happen, yet Meg must choose all the right things on her own for the events to take place. She is able to have total freedom within those foreseen events because she can always choose which path she goes down. This wrestling match between fate and freedom recalls writings of Boethius and Augustine on how God can know and have power over everything, yet people can still be free.
The time comes for Meg to leave for Camazotz. She thanks the beasts and Aunt Beast, embraces her father lovingly, and, to her surprise, receives a kiss from Calvin. Again, the Mrs. W's each give Meg a gift for her journey. Mrs. Whatsit simply gives Meg her love, Mrs. Whatsit's love for her. Mrs. Who gives her a quote from Scripture of which the first line is: "The foolishness of God is wiser than men; and the weakness of God is stronger than men." Mrs. Which then tessers with Meg to Camazotz, leaving her on the same spot outside the town at which the children had first arrived, and gives Meg her gift, which is the knowledge that Meg has something that IT does not have…but Mrs. Which says that Meg must be the one to discover what that thing is.
The gifts from the great Mrs. W's this time are entirely immaterial, emphasizing the power of words and, above all, love: Mrs. Whatsit's gift of her love will prove to be the most important. Mrs. Who's quote from Scripture is another reminder that man's best shot at omnipotence—a giant brain like IT that "knows" everything—is still not as powerful as the foolishness of God, and God is love.
Meg braces herself and sets out for the domed building where IT is waiting. All too soon she arrives, the building sucks her in, and she feels like the wind has been knocked out of her as the overpowering rhythm of IT begins to take over her lungs and heart…but she fights. Even more painful is the sight of Charles, whose blue eyes are still slowly twirling and who is crouching, slack-jawed by IT. When she appears, he begins to speak to her coldly and cruelly, telling her that Mrs. Whatsit is on ITs side and other lies. Meg begins to hate this Charles so much that she begins to be absorbed in IT (who is also all hatred). IT then makes the fatal mistake of telling Meg through Charles that Mrs. Whatsit hates her. Remembering Mrs. Whatsit's gift of her love, Meg immediately denies this, and then in a flash realizes what she has that IT doesn't: love.
Here, love comes out as the most powerful and redeeming idea and thing in the novel. IT, who is so strong and controlling and all-knowing, lacks one huge thing that a puny teenage girl has: love. IT can't know love because it has nothing to love. IT seeks control and domination, and therefore sees all others with contempt, with hate, as deserving to be controlled. And IT creates sameness and there can be no communication between sameness because there is nothing to share. It is difference that creates the foundation for love, weakness that allows for love, and love is then the respect for those that are different, that are weak in their own ways, and a willingness to trust those others, and to care for them, to want to communicate with them.
Meg stands there, gazing at Charles, and loving him. She focuses not on IT, but on her own brother who she loves more than anything else in the world. She directs her love so powerfully towards Charles that, slowly, IT is forced out of him. And suddenly Charles rushes into her arms, sobbing her name, and, after the abrupt and cold feeling of a tesseract, they find themselves back home in the Murry's backyard, along with Calvin and Mr. Murry! The twins and Mrs. Murry come out at once to investigate the ruckus, and they all share a joyful family reunion. Suddenly the Mrs. W's appear, deepening their joy. Mrs. Whatsit apologizes for failing to say goodbye earlier, and mentions that they are already involved in a new mission. But before Mrs. Whatsit can explain what the mission is, there is a gust of wind and all three of them vanish.
In the end it's not Meg's advanced intellect that saves her and Charles, but her tremendous love for Charles. The novel ends with an outpouring of familial love between all the Murrys and Calvin, showing that the triumph of good over and evil is effected by family member's love for one another, which is shown to be a wonderful, joyful reality. The presence of the Mrs. W's even at the end is a fitting bookend to their journey together with the Murry children, but also emphasizes how much they are like traveling angels who move on from one mission to the next in the fight against the Black Thing.