As his eye travelled back across this wing, in his lively walk towards the stable, he caught a passing glimpse of a nurse's face and figure in one of its upper windows.

This located the sick chamber, and unconsciously he hushed his step and moved with the greatest caution, though he knew that this sickness was not one of the nerves, and that the loudest sound would fail to reach ears lapsed in a blessed, if alarming, unconsciousness.
Once around the corner, he resumed a more natural pace, and perceiving that the stable-door was closed but that a window well up the garden side was open, he cast a look towards the kitchen windows at his back, and, encountering no watchful eye, stepped up to the former one and peered in.
A man sat with his back to him, polishing a bit of harness.

This was probably Zadok, the coachman.

As his interest was less with him than with the stalls beyond, he let his eye travel on in their direction, when he suddenly experienced a momentary confusion by observing the head and shoulders of Hexford leaning towards him from an opposite window--in much the same fashion, and certainly with exactly the same intent, as himself.
As their glances crossed, both flushed and drew back, only to return again, each to his several peep-hole.

Neither meant to lose the advantage of the moment.