Thinking over the possible way by which Harry Feversham might have redeemed himself in Willoughby's eyes from the charge of cowardice, Durrance could only hit upon this recovery of the letters from the ruined wall in Berber.

There had been no personal danger to the inhabitants of Suakin since the days of that last reconnaissance.

The great troop-ships had steamed between the coral reefs towards Suez, and no cry for help had ever summoned them back.
Willoughby risked only his health in that white palace on the Red Sea.
There could not have been a moment when Feversham was in a position to say, "Your life was forfeit but for me, whom you call coward." And Durrance, turning over in his mind all the news and gossip which had come to him at Wadi Halfa or during his furloughs, had been brought to conjecture whether that fugitive from Khartum, who had told him his story in the glacis of the silent ruined fort of Sinkat during one drowsy afternoon of May, had not told it again at Suakin within Feversham's hearing.

He was convinced now that his conjecture was correct.
Willoughby's reticence was in itself a sufficient confirmation.
Willoughby, without doubt, had been instructed by Ethne to keep his tongue in a leash.

Colonel Durrance was prepared for reticence, he looked to reticence as the answer to his conjecture.