The film is loosely based on the real-life pirate, William Kidd. Born in Scotland in 1645, he began his career as a privateer. By 1690 he became a wealthy shipowner in New York. In 1696, during a trip to East Africa, he turned to piracy. He captured or looted many ships. Trusting that his privateer commission would protect him, he returned to Long Island in 1699. He was ordered to England, where he was arrested, tried and convicted for piracy and murder. He was hanged in 1701. Stories about Kidd's buried treasure were legendary but the only booty ever found was on Gardiners Island, near Long Island, in New York.
Four years before this movie was made, Charles Laughton co-starred in It Started with Eve (1941), In that film, Laughton's character, Jonathan Reynolds Sr., is said to have been born two centuries too late. The assistant newspaper editor comments that he could have been "Captain Kidd himself".