SPOILER ALERT: If you have not read BATMAN #13 yet and do not wish to know what happens, stop reading this post now (major spoiler alerts ahead!).

The Joker was taking it back to the beginning. Acme Chemicals. The catwalk. The Red Hood.
 
The stage was set for the first of what promised to be a cataclysmic series of battles between the Dark Knight and his arch-foe in BATMAN #13, writer Scott Snyder and artist Greg Capullo’s cinematic kick-off to the line-wide “Death of the Family” Batman crossover.
 
But seconds before Batman reaches the Red Hood, he’s knocked into an empty chemical vat and left to discover that it isn’t the Joker underneath his old duds, but his sometimes-sidekick Harley Quinn. But why?
 
Why else? To trick, delay and distract Batman while the Joker himself is off wreaking havoc elsewhere.

Where? Well, you should read the issue. Seriously. BATMAN #13 is as important as these things get, and it’s a thrilling kick-off to what’s sure to be the most talked-about Batman story in decades. Yup. Decades. If you haven’t read it yet, please make a beeline to your comic shop now. We’ll wait here.
 
And if you had any doubts that this Joker is a meaner, deadlier and more frightening version of the Clown Prince of Crime, they will be quickly dispelled by Harley’s chilling response to Batman:
 
“He’s not the same, Bats…He’s not my Mr. J. anymore.”