Claudia is the main character from whose perspective the story is told. She is 14 when Monday Charles, her best friend, dies, and she is 16 when the novel ends. Because of shyness and a learning disability (dyslexia), Claudia has only one friend: Monday. Claudia loves to dance; she and Monday spent hours choreographing routines together. She is also very attached to colors, a characteristic of her learning disability, and sees everything in their shades. (Her father buys her intricate coloring books because coloring helps her anxiety.) 

When Monday disappears, Claudia is the only one who grasps the gravity of the situation. She desperately tries to get adults to help her find Monday with minimal success. Not even her parents comprehend that Monday is in mortal danger. All the while, Claudia must figure out who she is without her friend. She becomes close to a boy from church, Michael, with whom she develops a romantic relationship.

After Monday’s body is found, Claudia has periods of dissociation, where she thinks Monday may still be alive. Because of this, her family pulls her out of public school, and she works with a private tutor. Her parents encourage her to continue dancing, and dancing helps Claudia find who she is without Monday.