One couldn't exactly put finger on it.

Something in his gray eyes, perhaps; something in the sharper stamp of his aquiline nose, of his lips, of his bronzed jaw; something in his whole bearing.

It went deeper than features, too; she sensed a change in the spirit of the man from what it had been that day of his going down to Kennard, when he strolled with her in her garden.

He was less bouyant, less manifest, less elated, but more poised and sure.

A change, yes.
Then her thoughts reverted to his tremendous undertaking.
"How long have you known this ?" she inquired.
"Since the day before yesterday.