They were falling. And Leslie was screaming.
Amidst the chaos, Atticus twisted his body and looked up. As it turned out, the three of them had been unknowingly standing on a trap-door. When Bentley pressed the button, she must have activated some mechanical network that caused it to open. That was the strange thumping sound they had been hearing. It was a classic trick, like something out of a cartoon. But they had fallen for it and now they were plummeting through another black void of unidentifiable size or depth. Good going, Bentley.