I can't.

If you are so doubting now, perhaps you had better not see me any more.

I want to be frank with you, but if you won't let me--" She paused heavily, gloomily, very sorrowfully, and Cowperwood surveyed her with a kind of yearning.

What an unreasoning pull she had for him! He did not believe her, and yet he could not let her go.
"Oh, I don't know what to think," he commented, morosely.

"I certainly don't want to quarrel with you, Stephanie, for telling me the truth.
Please don't deceive me.