Following his banishment from England for aiding an injured enemy, physician Peter Blood (Louis Hayward) resorts to piracy, becoming captain of a notorious crew of buccaneers. Sent to capture Blood is the Marquis de Riconete (George Macready), a brutal man willing to do whatever it takes to bring in the wanted swashbuckler. After Riconete finally catches Blood's crew on an island, Blood must go incognito to rescue his men, all with the help of Riconete's niece Isabelita (Patricia Medina).