How should Polly know about him?
It seems to me a most unlikely thing--the most unlikely thing I ever heard of.

I shall never believe it till she's proved her words.

I won't believe it--I can't believe it--never!" Her voice rose on tremulous notes, her eyes wandered disdainfully.

She looked at Gammon and immediately looked away again.

He, as though in answer to an appeal, spoke with decision.
"What we're here for, Mrs.Clover, is to put Polly face to face with you and so get the truth out of her.