Fifteen years ago, a mugger named Joe Chill accosts Thomas and Martha Wayne and their young son Bruce. He shoots Thomas and Martha and leaves Bruce to survive. Bruce vows to avenge his parents and spends the following years developing his mind and body. One evening, while sitting in his father's study, a huge bat flies into the window. Believing it to be an omen, Bruce decides to drape himself in the trappings of a bat, and thus the Batman is born.

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The Joker announces on the radio that he will kill Henry Claridge and steal the Claridge diamond at midnight. The police guard Claridge but he died anyway at midnight with a smile on his face. The police then discover that the diamond was stolen and that it was replaced with a glass one. Later the Joker announces that he will kill Jay Wilde and steal the Ronkers Ruby. The Joker succeeds with that too. But a mobster named Brute Nelson who is enraged that the Joker is pulling off all these jobs that he planned sends word out that he thinks that the Joker is a coward. Bruce Wayne and Dick Grayson hear about this and suspect a trap so Bruce as Batman goes to the mobster's house. The Joker is also there and he shoots and kills Nelson but he is pursued by Batman. However the Joker gets the upper hand by knocking Batman off a bridge. Luckily Batman survives. The Joker then resumes his work by announcing that he will kill Judge Drake. The Joker impersonates the police chief and kills the judge. The Joker also discovers Robin outside and kidnaps him but Batman soon saves him.
The Joker manages to escape and Robin then tells Batman that the Joker was saying that he was going after the Cleopatra Necklace. They then defeat the Joker and send him to jail.

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Professor Hugo Strange returns with a growth formula that changes asylum inmates into 10-foot tall "man-monsters" that wreak havoc on Gotham City. Batman is captured and injected with the serum, but manages to escape and create an antidote. Batman then punches Strange out the window into the murky waters below. Batman then pilots the Batplane and kills many of Strange's henchman and some of the monsters with machine-gun fire. He also manages to hang one of the monsters with his Batrope. He finally kills the last monster by throwing tear gas pellets while it is atop a skyscraper, causing it to fall to its death.

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