Isle of Forgotten Sins is an American South Seas adventure film released on August 15, 1943 by PRC, with Leon Fromkess in charge of production, directed by Edgar G. Ulmer (also credited with original story) and featuring top-billed John Carradine and Gale Sondergaard, whose performance in one of 1936's Academy Award for Best Picture nominees, Anthony Adverse, earned her the first Academy Award for Best Supporting Actress.

[1] Third-listed supporting actor Sidney Toler worked on this PRC title between the finish of his Charlie Chan films at 20th Century Fox and just before their resumption at Monogram Pictures.

The film features several songs (with Carradine singing "Whiskey Johnny"), an underwater sequence using a marionette and a tropical monsoon climax.

On a boat moored in the harbor, deep sea diver Mike Clancy awakens from drunken sleep to find that his diving partner Jack Burke has tied him to the bunk bed.

After Burke comes to, Clancy says that he has recognized two guests in the room as Krogan and Johnny Pacific, the captain and purser of the steamship Tropic Star which, six months earlier, disappeared in the Coral Sea with three million dollars in gold.

After he and Burke leave Marge's place, a scream is heard from upstairs, then a shot, and a customer staggers and falls from the upper landing, dead.

In fact, the map has been placed there for Burke and Clancy to find; Krogan's plan is to lure them into doing the hazardous work of recovering the gold which he will then seize for himself.

At "The Bird Cage Cafe", Marge is later seated at the cash register, with a framed photograph of Diane and Burke as a happy couple, propped up against it, while Clancy, wearing a captain's cap and jacket, sits by her and says, "I'll have to put the bite on you for about fifty dollars", explaining that he will tell her more later, adding, "you haven't forgotten about that bungalow on the Riviera, have you?"

[6] Leonard Maltin's Movie Guide (2001 edition) gives Isle of Forgotten Sins 2 stars (out of 4) calling it a "standard programmer", but concludes that "as usual, Ulmer's direction is much better than the material".

Also assigning 2 stars (out of 5), The Motion Picture Guide (1987 edition) describes it as "a jumpy and only partly engaging picture that seems to have been rearranged thanks to the Hays Code, this film had one of the best casts ever put together by poverty-row PRC", and the specialized 1996 compendium, Michael J. Weldon's Psychotronic Video Guide, has a brief two-sentence write-up which mentions the plot and cast, along with notation that "Carradine starred in Ulmer's better-known Bluebeard, also from PRC".

Sections focusing on themes in Isle of Forgotten Sins common to Ulmer's work are highlighted by sub-headers: "Technical, Constructivist Worlds", "Telling the Story with Light", "Weather", "The Night Club", "Modular Architecture", "Figurines", "Tilted Camera Angle", "Characters", "The Finale" and "Uniforms."