The Joker is aided in his Halloween quest to render modern technology useless and take over Gotham City by Solomon Grundy, Silver Banshee, Clayface and Scarecrow.

A million years ago in Africa, the last of the Australopithecines is on flight from the humans, who killed the rest of his clan. Alone, seeking others of his kind, he traverses steppes, deserts and mountains until he reaches the c...