He found that the havildar had spoken truly. There was no lack of volunteers. He soon arranged his little party of twenty, and posted them in the shelter of the wall until the time should come for letting down the bridge and leading them across it. The minutes passed very slowly. Lawrence would not think it necessary to push his reconnaissance as far as the enemy’s encampment. He might perhaps fly thirty miles, and then return. This would take something less than an hour. If he should discover the field guns within a short distance of the mine, the explosion of his bombs might be expected much earlier. Half an hour passed. There had been no sound from up stream; no sign of activity among the enemy. Bob began to feel more hopeful. They had apparently met with great obstacles to the passage of the guns. He was momentarily expecting to hear the hum of the returning aeroplane when, with a suddenness that took him all aback, there was a tremendous roar, followed in a second or two by a terrific crash just beyond the Pathan compound. Turning in consternation to discover the cause of it, he saw a great mass of the cliff falling amid a cloud of dust and smoke upon the wooden pathway, and plunging into the river beneath. Such destruction could only be the effect of a shell. Beyond doubt one at least of the field guns had been brought into position behind the enemy’s breastwork at the bend. This fact filled him with as much dismay as amazement. It was not surprising that the enemy had placed their gun without his knowledge. They would, of course, have been careful to mask it until they were ready to open fire. But why had Lawrence or the Gurkha not seen it? Could it be that the aeroplane had been damaged and brought down after all? While he was in a painful state of anxiety, there was another roar, and a second shell burst on the cliff, just beyond the Pathan gallery. He ran to the northern wall and peered through one of the loopholes. Smoke hung above the enemy’s breastwork, but there was not a man to be seen, so that rifle fire was useless. He ordered Gur Buksh to fire the machine gun. The havildar’s aim was good; chips of rock flew from the breastwork; and Bob thought he saw the muzzle of a gun disappear. His attention was immediately drawn from it by the sight of the aeroplane flying round the bend, and with the thrill of relief at his brother’s safety came the expectation of hearing an explosion and seeing signs of havoc about the breastwork. But the aeroplane flew high over the scene, passed it, and disappeared up the river. There had been no explosion. Why had not Lawrence dropped a bomb?