The film follows British Navy Lieutenant Robert Maynard, who sets out to earn a reward by proving that privateerHenry Morgan also engages in piracy. Maynard poses as a surgeon on board the ship of pirate Charles Bellamy, who he believes is in league with Morgan. Once Maynard and fellow spy Briggs come on board, they discover that the pirate Blackbeard has murdered Bellamy and taken over as captain. Also on board is Edwina Mansfield, a pirate's daughter, who was going to marry Bellamy. Blackbeard knows that Morgan loves Mansfield and will pursue her. Blackbeard orders Maynard to remove a bullet from his neck, and demands sailor Gilly watch him. Gilly slips Maynard a note begging him to slit the pirate's throat, but Maynard declines. Maynard slips into the Blackbeard's quarters and finds Bellamy's logbook, which he hopes will contain evidence that Bellamy gave Morgan stolen goods. Maynard then defends Edwina against the unwanted advances of a lecherous pirate, killing him with his dagger. She tells Maynard that she agreed to marry Bellamy to escape from Morgan, from whom she has stolen treasure, which is now hidden in a clothes chest. Blackbeard breaks open one of Edwina's chests but discovers only letters in which Edwina implicates Morgan as Bellamy's ally. Maynard tries to steal the letter, but Blackbeard stops him, noting that if Morgan were arrested, all of his loot would go tothe King. Blackbeard finally identifies the treasure chest and claims it.
The film was based on an original story by DeVallon Scott. It was on the schedule at RKO for 16 months before being taken over by producer Edmund Grainger for his independent unit. It originally conceived as a vehicle for Faith Domergue. It was going to be filmed under the title Buccaneer Empire by director Robert Stevenson. Several months later RKO announced the lead would be played by Robert Newton, who had just enjoyed success playing Long John Silver in Treasure Island. Production took a while to begin; for a time it seemed Newton might be replaced by Charles Laughton. Alan Le May was hired to rewrite the script shortly before filming began on 15 May 1952.
