"Calling that art is more of a reach than I believe you're capable of," Childermass says, sounding indifferent about it even in spite of how, yes, that is something he drew himself. "So I can tell you now you're a bit off in your guess."

He won't, however, be helpful and tell him why nor what the Ringmaster actually is. If the man wants to play guessing games, he's free to keep at it, regardless of whether or not he believes what he's saying himself. As for Childermass, he just idly taps the pen in hand against the page he'd been working on, finally taking the time to size Lambert up. He'd been dismissive before, but if this guy is going to stick around and try to be annoying...

"But you are right about one thing. It wouldn't be the craziest thing to happen around here."

It's also not a thing at all, but why tell Lambert that?