The Cay is the suspenseful story of a young boy, handicapped by blindness and thrust into an unfamiliar environment, who is forced to grow up quickly.

Young readers can identify with Phillip's struggle for independence and his frustration in coping with situations over which he has virtually no control.

Phillip's survival depends upon his learning to follow Timothy's instructions and to respect the power of nature. He jeopardizes his life each time he forgets past lessons, but those lapses—whether from carelessness, fear, or despair— make Phillipa very believable character.

The Cay illustrates Phillip's progress toward an ideal of tolerance, chronicling the course of events that gradually leads him to shed his prejudice toward Timothy. At first Phillip considers himself superior to Timothy, an old black sailor who eats raw fish and cannot spell the word "help." He depends upon Timothy but keeps both a physical and an emotional distance. Slowly, though, Phillip begins to appreciate Timothy's kindness and wisdom, and at the end of the novel he plans a significant gesture of respect—a pilgrimage to Timothy's grave.

Set in the Caribbean, close to the South American mainland, the novel provides an unusual perspective on historical events and topics frequently overlooked, such as the role of the merchant marine during World War II, and the war's impact on domestic life in the Americas.