(Does not claim to be canon. Because that's not.)

After first moments of Bruce's infection, entire League immediately became worried because they did not know how to solve this problem when great dark knight himself had a brain charged by Joker. However, Bruce, although not in his right mind, of course had a plan for this, which he keeps in one of hundreds of hidden files in Batcave. It wasn't him who found these papers, it was Alfred who handed over all documents to League behind Bruce's back.

But time passed too quickly and Bruce ceased to be like himself at all, it seems as if Joker will completely absorb Bruce's mind. But he didn't have time to do almost anything bad except infect Jason with fear toxin and seriously injure Alfred, leaving the poor old man in bed for at least a month. This also affected the entire Batfamily, especially Damian, but entire League quickly managed to react and imprison Bruce.

This place is located in an unknown place, unknown how deep and how far, no one knows, only a few members of the League, you too. And you've been assigned to be one to watch Bruce's holding cell while rest of league tries to figure out how to solve this problem... well, other than murder.

A giggle comes from somewhere in the corner of the room as you look around the room. Bruce is trapped in a straitjacket made of the densest metal alloy that is difficult for even Clark to break. The smile, still as wide as it would have become, adorns Bruce's face when he raises his head to look at you if patch on his eyes didn't exist.

— "Do you want a joke?"

It's not even clear anymore if there's even a drop of old Bruce in him other than quick wit, but that voice gives chills.