Three down-on-their-luck beatniks -- John Mapes, an aspiring actor; Ray Miller, a failed writer; and "poor little rich boy" George Leland, the neglected son of a famous movie star -- are hired by an amoral coffee house proprietor to help pull off an armored car robbery during a rail trip. The heist goes off swimmingly; but afterward, on the train to New York, the conspirators begin dying, one by one.

"My plan hinges on the interesting fact that if you take a train from Los Angeles to New York, there's a four-hour stop-over in Chicago."
"What's so interesting about Chicago?"
"Any town where you steal a million dollars is interesting."

For the Mystery Science Theater 3000 episode see here.

Tropes used in The Rebel Set include:

"Father" Tucker: What makes you think it was suicide?
Conductor: What else would it be?
"Father" Tucker: Murder?
Conductor: What makes you say that?
"Father" Tucker: This [suicide] note is type-written.
Conductor: Well?
"Father" Tucker: Where's the typewriter?

Servo: [upon seeing Leland for the first time] Hey, guys, you know who that is? I sing when I sing when I..."
Crow: Oh no!

    • And Edward "The Chief" Platt as Tucker.
    • And Gene "Not Merritt Stone" Roth, of course.
  • I Thought That Was: While not as bad as The Beatniks, the protagonists are more accurately described as "beat" than "rebellious".
  • Missing Mom: Rita Leland provides her son George with all the Freudian Excuse he could possibly ask for.
    • She does finally decide to (very publically) reconcile with George at the end... while not noticing his corpse being wheeled past her mid-speech.
  • The Mountains of Illinois
  • Murder Is the Best Solution. "One less share to dispense, and now... there'll be still another share less."
  • Paper-Thin Disguise: A clean shave and a priest's collar.
    • The episode guide notes that the first time the MST crew watched the film, it took them all quite a while to realize it was supposed to be a disguise.
  • Porky Pig Pronunciation: "Did I see you adulterat... adultering... oh, spiking that Coke?"
    • Actually botched; if you listen closely you can hear the actress pronounce "adulterating" correctly both times.
  • Sesquipedalian Loquaciousness: Tucker. When confiding with his main man Sidney, nearly degenerates into an Expospeak Gag.
  • Shallow Love Interest: John's wife Jeanie. No, not that Jeannie.
  • Smart People Play Chess: Tucker at the start of the movie. According to him he rarely loses, but only because he makes sure to play against bad chess players.
  • Stop or I Will Shoot: The cops have no qualms about shooting a fleeing man in the back. To be fair, they think he's a murderer.
  • Tap on the Head: A particularly Egregious example.
  • Trick Dialogue: We are introduced to the lead character, John, who is in the midst of a melodramatic argument with an off-camera woman. The woman turns out to be an actress' voice-over on a "learn how to act" record collection.
  • The Windy City: Chicago, where the robbery takes place during the train layover.