Something funny is afoot in Gotham City, but Batman and Batwoman aren't laughing.

Robbery victims are handing over their loot and seem downright delighted to do so.

While investigating this odd behaviour, 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 Batman and Batwoman get to the bottom of the jester's joke before the punchline knocks out half of Gotham City?

Find out in this action-packed chapter book for DC Super Hero fans.