Batman: Gotham Knights

You sit in the Batcave, intently watching the Batcomputer and listening into all the radio channels. Finally, the television snaps on with the Joker's smiling face.

"Hello, Bats!" he laughs, "It was hard to get this direct connection, but I finally got through! Guess we've been playing tag... but then, that's how it always is. I'm sure you've heard that Bane broke me out of Arkham... oh wait, sorry. Hearing "Bane" and "Broke" together doesn't sit right with you, yes? Ah well. Hoo hoo hoo! I'm back at Arkham anyway. I've rigged the entire place with four big ol' plastic explosives that'll go boom in about an hour... unless you can come down here and defuse the bombs, of course. And just for insurance, I've got Mr. Jeremiah Arkham himself here with me, held at gunpoint by the lovely Ms. Quinn! Say hello, Harl!"

"Um... hiya!" Harley Quinn squeaks.

"Ain't she a doll?" the Joker smiles, "Anyway, hope to see ya soon, Batty McBatterson! Love, the Joker!

P.S. - Come alone, or I might just blow it up before time's up!"

Well... this is certainly not good, you think. The Joker's the most dangerous enemy you have. It doesn't help to ask why he does these things, you can't get into his head... he's just plain crazy.

You have very few options. What do you do?