Why is this lady telling me she knows everything?!?
My dear child, do not fear, I am here to help. May I have some food?
Mrs. Whatsit barges into the kitchen looking for Charles. Meg heard them talking about the tesseract, she knew that Mrs.Whatsit could help with the location of her dad. Charles knew something she didn't. Calvin O'keefe somehow fit into the picture. Mrs. Which asked for food then later explained everything. She needed this for herself and her siblings.
Mrs. Who, Mrs. Which, and Mrs. Whatsit had tessered to another safe planet, free from darkness, to explain the mission. Confused, Meg, Calvin, and Charles chose to listen. Little did they know Mrs. Who used to be star, fighting the darkness, she knew how to defeat it. The plan had been created. They were going to save father.
Charles Wallace, Meg, and Calvin made their way to Camazotz, the planet where IT was living. The Man with the Red Eyes had greeted them with a surprise of "turkey dinner". Charles trusted this mysterious man, he was soon hypnotized. Anything the man believed Charles would enforce it upon Meg.