Sean Flynn plays Robert Blood, the son of Peter Blood, an Irish doctor-turned-swashbuckler in 1936's Captain Blood (starring Flynn's father, Errol). Robert is a young man who, like his father, hears the call of the ocean. His mother would like Robert to stay and become a doctor rather than face the dangers that Peter had once faced on the sea. Unheeding, Robert sets out and immediately joins a ship's crew. It is there where he meets an old enemy of his father, De Malagon (Jose Nieto), who pirates onto the ship and proceeds to give Robert what-for on account of his heredity. Coming to the rescue is the pack of his father's old sea-pals who transport Robert and his beautiful passenger Abbigail (Alessandro Panaro) to safety. Soon, however, Robert finds that danger lurks everywhere and he and his new friends continue their adventures.