a warning to look out ...

it's often simply the effects of building up; and we're beginning to think--ah! that won't interest you! Listen to me! I'm what they call a specialist--an investigator.

I can tell you, without conceit, that I probably know all that is to be known on a certain subject.

Well, I can tell you as an authority--" Frank lifted his head a little.

He was keenly interested by the fire with which this other enthusiast spoke.
"I daresay you can," said Frank.