Marlene Dietrich stars as Helen, a German actress and singer who meets and marries American scientist Edward Faraday (Herbert Marshall). She moves to New York with him and gives birth to a son, Johnny, while Edward works on his (unspecified) dream project. But five years later, Edward discovers that the chemicals he's been working with all these years have poisoned him, and he will die unless he goes back to Germany to get an experimental treatment. The trouble is, Edward doesn't have the money.
Helen talks her reluctant husband into letting her return to the stage to raise the funds, and she gets a job at a cabaret, where she's billed as "The Blonde Venus". There she attracts the interest of millionaire Nick Townsend (Cary Grant), and begins to accept money and gifts from him while pretending to her husband that it's coming from her employer. When Edward finally leaves for Germany, Helen realizes that she has feelings for Nick, too, but insists that she has to return to her husband when he's well. Unfortunately, Edward returns from Germany earlier than expected...
Blonde Venus contains examples of:
- All Men Are Perverts: This movie just takes this as an uncontestable assumption. Even Edward, the family man, gets a date with Helen by spying on her while she's skinny-dipping, and refusing to leave until she agrees to see him again.
- Beauty Is Never Tarnished: During the second half of the movie, Helen flees with Johnny in increasing destitution, but her makeup stays perfect. Her clothes get ratty, but in a chic kind of way.
- Blackface: One of the movie's biggest moments of Values Dissonance for the modern viewer is the musical number "Hot Voodoo", in which a troupe of white chorus girls dress up in pseudo-African costumes with enormous Afro wigs, while Dietrich comes on stage in a gorilla costume.
- Bowdlerize: An in-universe example: Helen and Edward tell Johnny a fairy-tale version of their first meeting as a bedtime story.
- Divorce Assets Conflict: Edward is determined to cut Helen out of Johnny's life, which results in her essentially kidnapping her son.
- Divorce Is Temporary: Despite everything, once Edward and Helen meet again, they agree to stay together.
- Drowning My Sorrows: After Helen returns Johnny to Edward, she gets totally hammered.
- Fanservice: We get this in the very first shot, as Dietrich's blurred naked body slips by under water.
- Gold Digger: Deconstructed. Other characters see Helen as this, but the film tells everything from her point of view and reveals her motivations to be sympathetic, even if her decisions are flawed.
- Gray-and-Grey Morality: What makes this such a pre-Code movie is that no one is wholly good or wholly bad, and it's far from clear what the "right" choices for Helen would have been.
- I Owe You My Life: Edward feels obliged to repay Helen, even though he can't forgive her methods.
- Keep the Reward: Edward repays Helen the money she acquired for him but still takes Johnny from her. She gives the money away to a stranger.
- Mammy: Helen meets a couple of these on the road who help her out.
- Meet Cute: Edward's voyeuristic first meeting with Helen is probably supposed to be this, though through modern eyes it seems pretty creepy.
- Musical World Hypothesis: Diegetic. Dietrich/Helen performs three numbers on stage over the course of the film, but the songs to some extent reflect the offstage action.
- Skinny Dipping: Helen and five other actresses are doing this in the Black Forest when Edward and his friends come across them.
- Social Circle Filler: The friends that Edward and Helen are with in the opening scene are never seen again. Justified in Helen's case, since she moves to another country.