The film is set in—guess where, yep, Algeria during the time when it was ruled by France. Pepe le Moko (Boyer) is a notorious jewel thief who has absconded to the capital of French Algeria. French authorities are perfectly aware that Pepe is in the city, but they can't touch him because he is secure in the "Casbah", the walled native quarter where French law counts for nothing and the police are powerless. Inspector Slimane, the local detective who is responsible for Pepe, goes so far as to enter the Casbah from time to time for friendly chats with Pepe.
However, all is not as well as it seems with Pepe. He chafes at confinement within the Casbah and longs to escape and return to his native Paris, but he knows that once he leaves the Casbah he'll be arrested. Into this mix comes Gaby (Lamarr), the gorgeous young fiancée of a fat American businessman. Pepe and Gaby soon fall in love. It soon becomes clear that the crafty Inspector Slimane plans to use Pepe's love for Gaby as a means to lure him out of the Casbah.
A remake of French film Pepe Le Moko, starring Jean Gabin, which was released just the year before. Star-Making Role for Hedy Lamarr in America. The look of this film and the general idea of a Mediterranean town with narrow, winding streets, filled with crooks and schemers, proved very influential in the making of Casablanca. The line "Come with mee to ze Casbah", said by Charles Boyer in the trailer but not in the film, became strongly associated with him anyway. Additionally, Charles Boyer's performance in this film would inspire cartoon character Pepé Le Pew. There was a remake of this film in 1948 entitled Casbah with Peter Lorre, Yvonne De Carlo, and Tony Martin.
- Adaptational Alternate Ending: The only change made to this film from Pepe Le Moko. In that movie Pepe kills himself rather than be taken to jail. The censors demanded that Algiers be changed to have Pepe shot by the cops as he runs off after the passenger ship.
- Chiaroscuro: Lots of shadowy mood lighting in the cramped rooms of the Casbah. Most dramatic in the scene where Pepe drags Regis into a room against his will, and the two are seen only as silhouettes for a while.
- Concealment Equals Cover: Averted. Pierrot takes a potshot at the cops through a window. In response a bullet comes right through the wall, narrowly missing his head. Pepe laughs at Pierrot's wide-eyed shock.
- Double Agent: Regis, an informer. He reveals to the French cops where Pepe is hiding out, but then send a warning to Pepe that allows him to escape arrest. Still later he participates in a scheme to trick Pierrot into leaving the Casbah in order to lure Pepe to come after him.
- Drowning My Sorrows: Pepe drinks heavily after Pierrot dies of a bullet wound from the French police.
- Finish Dialogue in Unison: Pepe and Gaby both wax nostalgic about their common hometown of Paris, mentioning their favorite neighborhoods, an exchange that ends when they both say "La Place Blanche" at once.
- Foreign Remake: Of French Film Pepe le Moko. And a highly faithful remake, except for the ending—in the French version Pepe fatally stabs himself rather than be captured.
- Gentleman Thief: Charming, debonair Pepe admits that he took to stealing jewels because he likes them so much.
- Go-Karting with Bowser: Although Inspector Slimane is powerless to arrest Pepe in the Casbah he's free to enter it and hang out with Pepe. The two even strike up a friendship. Eventually Slimane leans on this when he tries to trick/goad Pepe into leaving the Casbah.
- Hero Antagonist: Slimane, who after all is only doing his duty in attempting to lure out and arrest Pepe.
- Hot Gypsy Woman: Maybe. Ines is never explicitly identified as a Roma, but she's dressed in the stereotypical Hot Gypsy Woman outfit and Norwegian actress Sigrid Gurie is clearly wearing some sort of tanning lotion. And she has the fiery temper of a Hot Gypsy Woman. (In Pepe le Moko she is explicitly called a gypsy.)
- If I Can't Have You : Pepe figures out the trap and might have made his escape on the boat, except for Ines going to the cops and telling them that Pepe was heading for the boat rather than the hotel.
- Naïve Newcomer: A policeman newly arrived from France indulges in a lot of blustering outrage about how the local cops haven't arrested Pepe even though they know where he is. This sets up some exposition in which Slimane and the other locals explain to the Naive Newcomer how the Casbah is so closed off and hostile that it's essentially impossible to go in and arrest someone.
- The Place: Algiers, where you can meet some interesting people.
- Rule of Three: After Pierrot is killed and Carlos gets arrested, Ines panics at the prospect of Pepe leaving the Casbah, saying "Bad luck always runs in threes!"
- Running Gag: Carlos the dimwit says something dumb. Pepe insults him. Carlos says "Say that again!", and Pepe repeats the insult. Carlos pauses and says "OK."
- Shot-for-Shot Remake: Except for a tweak to the ending this film is a near-exact copy of Pepé le Moko, almost as if the writers simply translated the French screenplay into English.
- Soundtrack Dissonance: Regis bumps into a player piano when Pierrot is approaching him, gun raised. So a cheery, upbeat piano number is playing as Regis is shot to death.
- Star-Crossed Lovers: A doomed romance between a businessman's trophy companion and a jewel thief, ending with the woman left in an unhappy marriage while the man is shot dead.
- Trophy Wife: Gaby's friend is the trophy wife of another obnoxious American businessman, while Gaby herself is a Trophy Fiancée. When her fiancé gets mad at her for sniffing around Pepe, Gaby says candidly that she's not marrying him for love and he knows it.
- Truth in Television: The Casbah really was a law unto itself in those days. A generation after this movie it would be a haven for the Algerian independence movement, as dramatized in the other famous film set in this town, The Battle of Algiers.
- Wretched Hive: The Casbah, filled with "filth" and "vermin", where criminals and ne'er-do-wells from all over the world gather, and where Pepe is immune from arrest.