高譚市本來正歡慶萬圣節之夜，忽然發生一連串神秘犯罪事件，迫使蝙蝠俠展開行動，追捕這群全市最惡名昭彰的壞蛋：稻草人，泥面人，銀嗓女妖和所羅門格蘭迪。唆使這群壞蛋的就是自稱犯罪小丑王子的小丑！他靠一個電腦病毒和邪惡計畫，將「數位笑聲病毒」散布至高譚市所有科技系統，.有黑暗騎士能阻止這幫惡棍的陰謀。蝙蝠俠和綠箭俠，生化人，夜翼還有紅羅賓合作，展開一連串驚心動魄的行動，設法阻止小丑的陰謀，并拯救高譚市。當太陽升起后，陽光將照耀在熟悉的高譚市，還是被邪惡佔據的小丑鎮呢？

It"s Halloween in Gotham. To celebrate, the city"s spookiest villains (Scarecrow, Clayface, Solomon Grundy and Silver Banshee) have all joined forces and gone on a crime spree. Batman swings into action to stop them, joined by Green Arrow, Cyborg, Nightwing and Red Robin. But it seems that the fiends are working for the clown prince of crime himself: The Joker, who has a surprise of his own - A computer virus that makes all technology laugh and obey his every command! Can the heroes stop the virus before it turns all of Gotham into Jokertown? Will Batman find a way to beat the Joker now that his trusty gadgets and vehicles have succumbed to "DIGITAL LAUGHTER?"