After school at Woodrow Roosevelt High, some students are in the gym; the basketball team is practicing for a big game, the cheerleaders are rehearsing their routines, and even Dick Grayson is there working out with some free weights. Susie, the chief cheerleader, decides they should take a break and goes to get some milk from the vending machine in the gym, but when she puts in a dime, the machine, instead of a carton of milk, dispenses twenty silver dollars. Most of the students are thunderstruck by what's going on, but principal Schoolfield is suspicious and calls Commissioner Gordon, who almost immediately suspects the Joker is the vandalous vendor and calls Batman on the hotline.
At Wayne Manor, Bruce is worried, knowing that Dick is already caught in the middle of the burgeoning tumult. He changes into Batman and rushes to police headquarters, where he finds out that Joker had been released from prison a week ago and immediately bought a company that makes novelty machines (pinball, gaming, gumball, vending, etc.). Batman has his suspicions as to what the Joker is up to, but before he can expound on them, principal Schoolfield calls Gordon to report that student morale is plummeting, and that another machine has been rigged; a candy bar machine in the school library now dispenses negotiable stocks and bonds. Batman directs Schoolfield to call an emergency meeting of the Student Council (for which Dick is president), and rushes to the school with a visual ID file on the Joker.
In Schoolfield's office, Dick is arguing with the rest of the Student Council members about what's going on when Susie goes to get a cup of coffee from the machine in the office, but instead of coffee the machine spews out a cupful of quarters. Their arguing continues until Batman shows up and warns them that the Joker is behind the rigged machines; he believes Joker is trying to deceive new recruits into dropping out of school and getting involved in crime. Batman then shows slides of Joker's mug shots when suddenly, out of nowhere, Joker himself pops up in the flesh. Batman is ready to arrest him for loitering on school grounds, but the Joker manages to get off on a mere technicality.
Meanwhile, across Gotham City, a cocktail lounge is held up by another gimmicked machine- a jukebox which, when a coin is inserted, activates a double-barrel shotgun and a recording of Joker saying "This is a stick-up!", then two stocking-masked hoodlums (who are actually the Joker's "Bad Pennies", Nick and Two-Bits, both high school dropouts), rush in to snatch the receipts from the cash register. Batman is called to investigate, and when Dick comes out to the Batmobile to return the ID slides, Batman quietly tells Dick to head to the Batcave and wait for him there.
The Joker reconvenes with Nick and Two-Bits at their hideout, the office and workshop for the One-Armed Bandit Novelty Company, hidden in the back of the Easy Living Candy Store, which is two blocks from the high school. Unbeknownst to everyone else, Susie is also a member of the Joker's gang. As chief cheerleader, she has an automatic seat on the Student Council, which gives her access to things non-council member students do not, and she is able to swipe some important exam papers for Joker.
Batman, having found no evidence at the lounge, returns to the Batcave. He and Robin discuss what to do next; They already know that Joker is behind the tricked machines, but they need evidence. Batman is convinced that the rigged machines at the high school are only a part of a much bigger scheme Joker has cooked up. They need to find out how Joker is getting into the school to fix the machines, so they decide to stake-out the school. At the school, Susie is rigging up another machine when she hears the Batmobile approaching. In a panic she calls Joker and asks what to do next.
Outside, Batman activates a remote radio pick-up and an anti-crime recorder in the trunk before they head into the school, where Susie pretends to be surprised and also glad to see the Duo. She tells them she saw someone suspicious lurking in the gym, where Robin shows Batman the rigged milk machine. Thinking that whoever rigged it is still there, Batman puts a dime in the machine, but instead of giving out silver dollars, the machine locks them in shackles and emits knockout gas.
When they come to, Batman and Robin have been moved to the inside of a mobile slot machine torture van, where they are strapped to electric chairs. Over a radio mic, Joker, sitting in the truck cab with Susie sitting next to him, announces to them that in a moment the three reels on the slot machine will start spinning. If three liberty bells come up, they will win their freedom and fifty thousand dollars. If three oranges come up, they will win only their freedom. But if three lemons come up (which Batman knows is the more likely), they will be instantly dispatched by 50,000 lethal volts of electricity. Joker guarantees the machine is honest, but when the reels start spinning, the first two stop on lemons...
- HORRORS!! ONE LEMON!!
- DOUBLE HORRORS!! DOUBLE HORRORS!! TWO LEMONS!!
- AND IF IT'S A THIRD...INSTANT AND INESCAPABLE 50,000 VOLTS!!
- CLOSE YOUR EYES! WHO DARES TO SEE IT?? TRY US TOMORROW! SAME BAT-TIME!! SAME BAT-CHANNEL!!