He looked through it.

In the giddy void white pigeons were wheeling in the dazzling sunshine, and, gazing down, he saw far below him, in the hot square, a row of booths, and troops of people moving to and fro like pigmies; and--and a strange thing, in the middle of all! Involuntarily, as if the persons below could have seen his face at the tiny dormer, he drew back.
He beckoned to M.Tignonville to come to him; and when the young man complied, he bade him in a whisper look down.

"See!" he muttered.
"There!" The younger man saw and drew in his breath.

Even under the coating of dust his face turned a shade greyer.
"You had no need to fear that he would let us go!" the minister muttered, with half-conscious irony.
"No." "Nor I! There are two ropes." And La Tribe breathed a few words of prayer.

The object which had fixed his gaze was a gibbet: the only one of the three which could be seen from their eyrie.
Tignonville, on the other hand, turned sharply away, and with haggard eyes stared about the room.