"That is precisely what I have been sent down to investigate," said his interrogator.
"We are all certain there's something going on," said the sentry, "though they ain't been seen for ten days now."
They stood side by side looking inland, and the staff officer, with his hands behind the back of his drab mackintosh, pressed the button of a tiny electric torch rapidly three times.
The sentry was only a boy, and he talked volubly, not heeding the melancholy call of a sea-bird from the water.
"Ah, well, I think we shall have them to-night," said the staff officer. "I see you have still got the old Mark II.?"
"Yes, sir," smiled the unsuspecting lad. "They took the others away from us when we came down on this job."
"Let me look at it," said the staff captain, holding out his hand, and the moment his fingers closed round the rifle the boy dropped senseless on to the stones, felled by a smashing blow from the heavy butt.
"You'll do!" said his assailant, and, laying the rifle down and gathering up the skirts of his mackintosh, he walked deliberately into the sea!
A collapsible boat, rowed by two men in German naval uniforms, was rising and falling on the top of the tide, and in another moment the men were pulling out into the rain blur with their mysterious passenger.
No one spoke, until the nose of the boat met the dark grey hull of the submarine waiting less than a quarter of a mile out, and as the beam of a searchlight suddenly flashed through the mist, the top of the periscope sank noiselessly beneath the waves, and Captain Von Dussel, alias Van Drissel, sank with it.