A first-person narrator recounts an adventurous sea voyage set in a series of episodic encounters that begin with an unexpected relative whose fragile temperament influences events. The small cruising vessel meets squalls, calms, and other ships, investigates derelict wrecks, and explores a volcanic island where a petrified hull and an ancient galleon are boarded. Rising tensions among those aboard, mysterious warnings, and nights of heavy weather and rescue attempts lead the narrative toward a tragic culmination, while the chapters trace the unsettling mixture of maritime danger, superstition, and human frailty during life at sea.