A high-society woman arrives on a Hawaiian island in search of Michael "Guns" Donovan, her long-lost half-brother and the owner of a local bar called Donovan's Reef. Upon meeting him, Amelia is taken aback by his rugged nature but also impressed by his kindness and intelligence. As they spend more time together, Amelia learns about Michael's past as an expatriate US Navy veteran who conducted guerrilla warfare against the Japanese during World War II, and she begins to see him in a new light. In the end, Amelia and Michael overcome their initial animosity and fall in love, with Michael even surprising her by revealing that he is actually her half-brother on her last visit to Boston.