Christopher Hadley Martin is a Royal Navy lieutenant who survives a torpedo attack on the HMS Wildebeest, washing up on a barren, jagged rock. Relying on his strong will to live, he methodically searches for water, shelter, and food to sustain his body. In his prewar life, he worked as a struggling actor. He approaches his survival with an adversarial mindset, driven by intense physical appetites and an overwhelming desire to conquer his harsh environment.

Mary is a young woman from Martin's life before the war who appears frequently in his thoughts. She possesses a natural, unconscious attractiveness that intensely draws Martin's attention. Her strict boundaries and refusal of Martin's aggressive romantic advances become a significant source of frustration for him.

Nathaniel is Martin's friend and a fellow sailor aboard the HMS Wildebeest. Known for his deeply philosophical and theological mindset, he delivered a lecture on the "technique of dying" and the concept of heaven before the war. His spiritual perspective heavily contrasts with Martin's intense reliance on physical endurance and materialism.

Pete is a theater producer from Martin's prewar civilian life. When military conscription begins, Martin attempts to use their professional relationship to gain assistance in evading the draft. Pete firmly refuses to grant him favors to avoid serving in the armed forces.

Helen is Pete's wife and an acquaintance from Martin's theater days. She engages in a clandestine relationship with Martin, who attempts to leverage their connection to influence her husband regarding his impending military conscription.

Alfred is one of Martin's civilian colleagues. His presence in Martin's memories highlights Martin's past behavior and his destructive tendency to mistreat those within his social and professional circles for personal gratification.

Sybil is Alfred's romantic partner in civilian life. She enters into a tryst with Martin, a memory that surfaces while Martin reflects on the aggressive, consuming nature of human appetites and his desire for interpersonal conquest.

Davidson is a British naval officer operating in the North Atlantic. He carries out his wartime duties with a pragmatic, official demeanor while managing the aftermath of naval incidents.

Mr. Campbell is a civilian who resides near a coastal island in the North Atlantic. He interacts with naval authorities and harbors deep, philosophical questions about survival, suffering, and the nature of endurance.