Get him to talk about it.

You can, and without rousing his suspicion, keen as they all say he is.

And when he talks, listen and remember what he says.

But don't ask questions.

Do this for me, Clifton.
Some day I may be able to explain my request, but not now." "I'm at your service," he replied; but he looked hurt at being thus set to work in the dark, and I dared say nothing to ease the situation.