What happens when a star dies in battle with the Black Thing? Why is the danger greatest for Charles Wallace?
Traveling with Mrs. Whatsit, Mrs. Who and Mrs. Which, the children see a burst of light in the sky. As the light, which is an exploding star, touches Darkness (the Black Thing), the Darkness disappears. A "gentle shining ... clear and pure" emerges where the Darkness once was. In driving out the Darkness, the star sadly gives up its life as a star. However, the consciousness of such a star continues in another form, as we learn that Mrs. Which, Mrs. Who and Mrs. Whatsit were once stars who gave up their lives to drive out evil.
Charles Wallace would also like to drive out evil, the evil of IT, which has taken possession of his father. Meg and Calvin hope to do this as well, but Charles Wallace is in the most dangerous situation because he doesn't have a strong sense of his own limitations. He is a very special, gifted little boy and is used to being smarter than everyone around him. Also, although he encounters nasty and catty people in his hometown, he has never encountered pure evil. In his pride, he overestimates his capacity to withstand the Darkness and so is overtaken.
In the novel A Wrinkle in Time, a star battles the Black Thing and partially obliterates the darkness. However, in doing so, the star dies. Charles Wallace, who has the gift of being able to enter people's minds, attempts to also obliterate the Black Thing by going into its mind to understand it. In doing so, however, Charles loses his sense of self and becomes trapped, almost completely under the control of the Black Thing. It was his perceptive gift of being able to completely read other people's minds that made him the most vulnerable.