Richard Widmark thought this was one of his worst films and used to tell his kids that if they didn't behave themselves, they'd have to watch it.
Jane Greer contracted a tropical virus during the location shooting of this film which eventually required her to have a heart operation. She also fractured her coccyx (tailbone) on a rock while filming the scenes in the swamp.
When Latimer is speculating about Browne's background, he talks about a British citizen broadcasting for the Germans during World War 2. This is a reference to the anti-Semitic Anglo-Irishman William Joyce ("Lord Haw Haw"), executed in 1946 for the Nazi propaganda he broadcast at the height of the Blitz. Browne himself is probably based on an amalgam of Lord Haw Haw and John Amery, leader of the British Freikorps.
This is a remake of RKO'S 1932 hit The Most Dangerous Game (1932). While the earlier version was filmed entirely on the studio back-lot (utilizing sets that later appeared in the original 1933 version of King Kong (1933) ) this version was shot mostly on location. And while the villain in the 1932 film was simply a madman, it is implied that Trevor Howard's character here is a former Nazi.
Although this is based on The Most Dangerous Game (1932), the biggest difference is that the hunters did not deliberately capture their human prey (i.e. game) in order to hunt them. Instead, the heroes just happened to crash land on their property, and later recognized one of them as a British traitor, and so they had to escape, and then were hunted for escaping, not as intended targets or prey.