.

The Marsh.
Athos and Monk passed over, in going from the camp towards the Tweed, that part of the ground which Digby had traversed with the fishermen coming from the Tweed to the camp.

The aspect of this place, the aspect of the changes man had wrought in it, was of a nature to produce a great effect upon a lively and delicate imagination like that of Athos.

Athos looked at nothing but these desolate spots; Monk looked at nothing but Athos--at Athos, who, with his eyes sometimes directed towards heaven, and sometimes towards the earth, sought, thought, and sighed.
Digby, whom the last orders of the general, and particularly the accent with which he had given them, had at first a little excited, Digby followed the pair at about twenty paces, but the general having turned round as if astonished to find his orders had not been obeyed, the aid-de-camp perceived his indiscretion, and returned to his tent.
He supposed that the general wished to make, incognito, one of those reviews of vigilance which every experienced captain never fails to make on the eve of a decisive engagement: he explained to himself the presence of Athos in this case as an inferior explains all that is mysterious on the part of his leader.

Athos might be, and, indeed, in the eyes of Digby, must be, a spy, whose information was to enlighten the general.
At the end of a walk of about ten minutes among the tents and posts, which were closer together near the headquarters, Monk entered upon a little causeway which diverged into three branches.