Riddler lures Batman and Robin to pose for marshmallow figures of themselves, on top of the giant cake to be presented for Batman's first anniversary of crime-fighting. But the top part of the cake is filled with 15 feet of quicksand!
"Is the party really over? Will Happy Anniversary be an epitaph for the dynamic duo?"
Batman remembers that the specific gravity of quicksand is close to that of water, and realizes that if they stay still they will not sink further than their shoulders. They carefully activate their heel-and-toe bat-rockets via the controls on their utility belts, and burst free of the quicksand.
While the city celebrates Batman's first year of crimefighting, Riddler plans to scatter all the molecules in the city!