As a last resource he must shatter her fine loyalty by an appeal to her gratitude.
"Rose, if some one you knew well--some one who had been the kindest of friends, and who had lent you a hand when you needed it most--were in danger, and I needed your help to protect--that person--would you tell me ?" Their eyes met; she looked away, and then, as she met his gaze again, her lips parted and the color deepened in her face.
"You don't mean--" she began.
"I mean that this is to help me protect a dear friend of yours and of mine.

I shouldn't have told you this if it hadn't been necessary.

It's as hard for me as it is for you, Rose.

There's a great deal at stake.
Innocent people will suffer if I'm unable to manage this with full knowledge of all the facts.

You think back, six years ago last spring, and tell me whether you have any knowledge, no matter how indefinite, as to where that letter was written." "You say," she began haltingly, "there's a friend of mine that I could help if I knew anything about your letter?
You'll have to tell me who it is." "I'd rather not do that; I'd rather not mention any names, not even to you." She was drying her eyes with her handkerchief.