SPOILER ALERT. I'm about to reference the ending of a venerable short story and a movie adaptation from the Golden Age of Hollywood. If you wish to read or view either of these in innocence, don't proceed further.
Old Hollywood had a rule that the bad guys never win. The evildoers always get their comeuppance. After all, if people wanted to see evil prosper, they didn't have to go to the cinema for that, they could just stick with the morning newspaper.
Anyway, the rule resulted in innovative re-writes to certain adapted literary works. This may never have been more jarring than in the case of Witness for the Prosecution, a 1925 Agatha Christie short story that had a complicated publication history over the next three decades and that became a movie only in 1957.
ONE FINAL WARNING. TURN BACK OR LEARN THAT ...
The basic plot of the short story is that of a criminal trial portrayed through the eyes of a sympathetic defense attorney, played in the movie by Charles Laughton. Laughton's character agrees to defend a man charged with the murder of a wealthy elderly woman.
The defendant is played by Tyrone Power in the movie. His wife, Christine, by Marlene Dietrich. [Those three names make up about as glittering a cast list as the era could offer.] At any rate, the defendant persuades his barrister (and the innocent audience) of his innocence, but whether the lawyer will be able to persuade a jury seems to turn on whether Christine will give alibi evidence.
Alas, Christine switches sides. She prepares to give contrary evidence as a "Witness for the Prosecution," hence the title.
In another twist, the barrister uncovers evidence that will allow for a devastating cross-examination of Christine.
The in-court show-down then plays out. Prosecution presents its surprise witness; Laughton devastates her credibility; jury brings in a verdict of not guilty. THEN comes the twist ending.
Dietrich confides in the barrister that she herself planted the evidence that he found and used to impeach her credibility, and she had gone to the prosecution planning to be discredited.
She couldn't take the chance of an honest unrigged trial, she says.
"Why, because you knew your husband was innocent."
"No, because I knew he was guilty."
THOSE words are the end of the story, and they work wonderfully, because Christie had been successful in luring us into the contrary conviction.
But as I've noted, Hollywood in the 1950s could not have a story end with a man getting away with murder. So there is a coda in which the barrister expresses his outrage, then the newly-acquitted defendant enters the discussion and tells Christine that he is leaving her for a younger woman. Christine stabs him with a letter opener (which had been an exhibit in the trial) and kills him.
The barrister immediately decides that he will defend Christine against the inevitable charge of murder, and the credits finally roll.
I really wish the creative people involved had found a way to evade the Code and make this movie without the Coda.