The Clown Prince of Crime, The Joker, attempts to undermine student morale at Woodrow Roosevelt High School in order to recruit high school dropouts for his gang of Bad Pennies by rigging the school vending machines to give out silver dollars and negotiable stocks and bonds instead of milk. Alerted by Commissioner Gordon, Batman races out to the school. An immediate assembly is made by the school's student leaders: including Richard "Dick" Grayson, Pete, and Susie, the school's head cheerleader. Batman shows up to show slides of mug shots of The Joker, when suddenly, out of the blue; he pops up right in full view of everyone! The Batman attempts to arrest him for loitering on school grounds, but The Joker manages to get off on a technicality. Meanwhile, across Gotham City, a bar is held up by a gimmicked jukebox which when activated sprouts a double-barrel shotgun; then two stocking-masked hoodlums, actually two of Joker's Bad Pennies, Nick and Two Bits, rush in to rob the bar's receipts from the register!
The Joker reconvenes with Nick and Two-Bits at their hideout, The One-Armed Bandit Novelty Company; unbeknownst to everyone else, Susie is also a member of The Joker's Bad Pennies! She arranges to swipe some important exam papers to that The Joker can use them in a blackmail scheme, and also leads The Dynamic Duo into a trap set by The Joker. The Homicidal Harlequin and his Bad Pennies snag The Duo with one of the rigged vending machines which, instead of giving out silver dollars, locks them in shackles and emits sleeping gas! Batman and Robin are transferred to the inside of an insidious moving van, where they are strapped to electric chairs; on the wall is a one-armed bandit, which when activated will release instant and inescapable 50,000 lethal volts of electricity should it turn up three lemons!!!!