Batman did not wait long. He turned to leave the surveillance room and stop Joker's plot, but just then, the surveillance room door, which had been open, suddenly slammed shut.
Like the doors of every room underground, the surveillance room door was made entirely of blastproof metal. Batman threw several miniature bombs at it, but they left only a few scorched marks and caused no further damage.
Batman was certain that the surveillance room door closing so suddenly was no accident. Yet he had not seen Joker make any extra movements on the screen. In other words, Joker might not have closed the door remotely. Someone else had done it.
Because Joker on the screen had been talking continuously, Batman could not be entirely sure whether footsteps had sounded during that time. If they had, it meant Joker had an accomplice.
Batman frowned as he thought. Earlier, they had been pursued by agents and had circled through the manor several times. During that time, Joker should have been sitting in the surveillance room, observing them in real time, because the agents had received information promptly. That proved Joker had been in the surveillance room then.
After the agents stopped chasing them, they made the plan to search for the entrance on the first floor. Immediately afterward, Batman began using helicopter parts to make bombs. Meanwhile, Joker found Lex and Clark and kidnapped them both.
The timeline matched up, but there was a huge flaw: if Joker had gone to kidnap Lex and Clark while Batman was making bombs, when had Joker made his own bombs?
Batman had clearly seen that the bomb that had made the noise and drawn the guests out was not small. Though its construction was relatively simple, it still would have taken time to make, not