He wants in short his own personal impression, and he'll get it--strong.

But as soon as he has got it Mamie won't suffer." "Oh Mamie mustn't SUFFER!" Madame de Vionnet soothingly emphasised.
But Strether could reassure her.

"Don't fear.

As soon as he has done with Jim, Jim will fall to me.

And then you'll see." It was as if in a moment she saw already; yet she still waited.