Something funny is a foot in Gotham City-but Bruce Wayne and Kate Kane aren't laughing. Robbery victims are handing over their loot and seem downright delighted to do so. While investigating this odd behavior, the Dark Knight and his crime-fighting cousin uncover the use of Joker Toxin. But the Joker is locked up in Arkham Asylum-or is he? Can Bruce Wayne and Kate Kane get to the bottom of the jester's joke before the punchline knocks out half of Gotham City?