The next morning, Meg tries to understand what happened the night before, hoping it was a dream, but Mrs. Murry steadily tells her that "one thing I've learned is that you don't have to understand things for them to be." The twins roll their eyes at how worked up Meg gets about some things, and Sandy tells her that she should use a happy medium with her feelings more often.
This is the first of many lessons given to Meg by her mother, as well as other wise people in the novel, that show her that there are some things that we limited human beings simply can't understand, and also that there are some things that are so profound that they simple can't be understood the way a math problem can. As such, instead of reacting with impatience, Meg must learn to accept what she can't understand, to value it, rather than ignoring it or denying its existence.
At school, Meg gets sent to the principal's office because of being sulky and belligerent in class. Mr. Jenkins, the principal, tries to convince her to give up her bad attitude but also somewhat nosily asks if she knows where her father is, even suggesting that she ought to stop hoping he's going to return. Meg tells him that she'll believe her father isn't coming home when her mother says so.
Mr. Jenkins can't comprehend Meg's implicit trust in her parents and in the love between her father and mother. His is the voice of skepticism, doubting that such a thing as true love can exist and implying that Mr. Murry has really just abandoned his wife and children.
When she returns home, Meg finds Charles waiting for her with a snack, Fortinbras on a leash, and a plan to go visit Mrs. Whatsit (who is staying, it turns out, in the haunted house not far from their property). Meg reluctantly agrees to go with him, and as they walk through the forest towards Mrs. Whatsit's house, they discuss Meg's day at school. Charles somehow already knows what happened to her, and shows a lot of love and understanding. When Meg asks him how he always knows what she and her mother are thinking, Charles tells her it's not quite like mind-reading, but more like "being able to understand a sort of language."
Here's another thing Meg will never fully understand: her younger brother's strange ability to know her thoughts and her mother's thoughts. Charles' knowing is a higher form of communication between humans, greater than just normal language. It also enables him to better understand and offer sympathy to his older sister, and Charles' love for Meg is to her invaluable.
As they near Mrs. Whatsit's house, Meg and Charles are surprised to run into a boy from Meg's school: Calvin O'Keefe. Meg only knows him as a talented basketball player a few grades above her who "fits in", just as she doesn't. Calvin is skinny and tall, with orange hair and bright blue eyes. He's in the forest, he reveals, because he had this intuition that he ought to come out to the haunted house. Charles, after staring at Calvin very hard for a while, somehow senses that Calvin is also "different" like himself and Meg and invites him over for dinner afterwards.
Calvin is another character who defies his appearance: though he is one of the cool, well-liked kids at school, he fits in by hiding his differences so well that Meg would never have known that he too has a special gift for communication and intuition like Charles.
The three of them approach the haunted house and don't find Mrs. Whatsit, but instead a friend of hers, Mrs. Who, inside. Mrs. Who is a plump, cheerful little woman with enormous glasses, sewing away at the stolen sheets to make them into ghosts for the haunted house. Mrs. Who often expresses herself by quoting great authors, frequently in different languages. When Charles asks Mrs. Who if she knows Calvin, she says, "He wasn't my idea, Charlsie, but I think he's a good one." Mrs. Who then mentions that Mr. Murry needs their help, though it's not yet time, and tells them all to go home to dinner.
Mrs. Who can't express herself well in the human language, and so she speaks mostly in quotes from great, classical authors, who have already said things so truly and wisely. Though she also looks innocent and maybe a little crazy, she too is nothing like her external appearance.
As the three of them return to the Murrys house, Meg is thoroughly confused. Charles doesn't know quite what's going on yet but says that he's sure Mrs. Whatsit and Mrs. Who can be trusted. Calvin is happy, feeling as if he's going home for the first time in his life.
Like the others, Calvin doesn't understand what's going on, but he does know that his friendship with Meg and Charles is a good thing, so he is happy in that.