Charles Wallace Murry is old enough to start school, but his sister, Meg, and their friend Calvin know he isn't cut out for school on Earth-Meg worries that he'll be more misunderstood than ever. Luckily, with the help of the three celestial creatures Mrs Whatsit, Mrs Who, and Mrs Which, there is another place where Charles Wallace can get his education: Intergalactic P.S. 3, a public school in a completely different galaxy. The three children travel through time and space to reach the school, but for them all to make it home safely, Meg must undergo a test that will challenge her inner strength, her perspective, and her ability to protect the ones she loves.