There's usually cracks in the walls- something that shows things ain't right. [He continues feeling the wall.] Wait. Maybe that's- no. That's an actual crack in the wall.

[He swears and backs up.] All right then. It's a good thing you're willin', Promptly, 'cause that's about the only way out. [If there was ever any doubt that it might be otherwise, he takes the time to kill that now, and then adds:] You know where you're goin', right? 'Cause I sure don't. Half-World's labs didn't look a thing like this.