Mrs. Which is a character from Madeleine L'Engle's novel, "A Wrinkle in Time." She is one of the three celestial beings known as the Mrs. Whatsit and Mrs. Who, who help the main characters on their journey. Mrs. Which is depicted as a wise and powerful figure, often appearing as a shimmering, ethereal presence. In the story, Mrs. Which guides the protagonists, including Meg Murry and Charles Wallace Murry, as they travel through space and time to rescue their father. Her ability to manipulate time and space is crucial in their quest against the dark force known as IT.