Caden’s story is split between dual narratives. In one reality, which corresponds to his time in the hospital under the influence of various medications, he is a sailor on a ship. In his other reality, he lives at home with his family, attends school, and occasionally visits with his friends Max and Shelby.

Caden’s life on the ship is a delusion. Gradually, his delusions begin to creep into his real life with an insistence that blurs the line between what is real and what is not. Caden knows that people are plotting against him and wishing him harm. He does not simply believe he can know people’s thoughts; he feels a strong conviction that he is inside their minds. He is wrong, but his certainty feels so concrete and urgent that he acts on his delusions as his compulsions flog him onward.

At the hospital, he begins to acquire tools that help him question whether something he sees, thinks, or feels may be a delusion. The ability to even wonder whether he is wrong gives him new insights into the nature of his reality. He openly worries about what he will believe next, whether it will be real or not.

The nonlinear plot of Challenger Deep blurs the line between reality and perception of reality. As such, it mimics the experience of someone with schizophrenia or a similar disorder: Something does not need to be factually true for a character who has schizophrenia to act on it. Hal’s delusions are not real, but he believes them to such an extent that he is willing to cut his own wrists; the delusions have become his reality. Even people who aren’t mentally ill often take action based on a warped perception of reality.

Finding alignment between what is real and what is perceived, arguably, can be one of the greatest challenges of human existence, even for typically functioning minds. Caden’s battle to hold onto what is real, and his determination not to be a victim, illustrates both his courage and the courage of all who do battle against mental illness.

One of the greatest challenges of mental illness—in the book and in real life—is that a person suffering from serious internal challenges may not manifest symptoms that are obvious to others. Caden’s thoughts, delusional and otherwise, are hidden from his parents unless he decides to share them.

Shusterman touches on the stigma of mental illness throughout the novel. In the hospital, Callie tells Caden that she is broken and not sure whether she can be fixed. When Caden says that dead kids are put on pedestals while mentally ill kids are swept under the rug, he articulates the denial that many people, from family members to society at large, engage in to avoid discussing or engaging with mental illness. A child who falls down a well or a person who develops cancer faces a specific challenge with specific approaches to treatment and resolution. Mental illness is a moving target that may ultimately prove insurmountable.

Because stigma often causes people who have mental illness to conceal their symptoms, and because so few people can relate to something as serious as schizophrenia, Caden never finds anyone who can empathize with his struggles until he is in the hospital. He recounts his impressions of a visit to New York City, where he wondered how people could feel so alone in such a crowded place, and says he now understands how they feel. His reluctance to describe his inner workings increases this alienation.

Caden’s parents try to communicate with him and to listen, but his answers to their questions are so off-kilter that they learn nothing from him, except for his symptoms. His angst is far beyond typical teenage melodrama, and his peers do not understand what he is going through. At the end of the novel, Caden knows that he is not cured, and he may face a day when he loses his fight. At least he knows he is ill. Unfortunately, people like Hal may never suspect that they could be delusional, and their ends can be disastrous.

The rotation of medications in the hospital, including the Risperdal, which produces a negative reaction for Caden, also demonstrates that the treatment of mental illness is not an exact science. It is an arduous, occasionally dangerous series of false starts, and trial and error.