Fifteen-year-old Caden is the protagonist and narrator of Challenger Deep who suffers from schizophrenia. In his fragmented reality, he experiences mania and schizophrenic delusions, and he self-aggrandizes his importance to an inordinate degree. He believes that he is being persecuted by forces he cannot see and that other people intend him harm.

After being hospitalized against his will by his parents, Caden struggles to acclimate to heavy sedatives, and he becomes aware of his inability to distinguish reality from fiction. Gradually, healing brings self-awareness, even though acknowledging his delusions does not make them go away. Rather, he gains tools that help him understand when what he is seeing may be false.

Caden is based on the author’s son, Brendan, who was diagnosed with schizoaffective disorder as a teenager. 

Caden’s parents are presented as fallible, loving, and relatively ordinary. They are helpless before Caden’s illness, with no clear understanding of what is happening to him or how they might help him. They know that what Caden says is false, but they have no way to convince him.

Caden sees them as people wearing masks for much of the novel, only pretending to be his parents. During his hospital stay, he realizes how much his behaviors and conditions affect them and how miserable their experience has been.