“Look!” whispered Beryl. “What is he doing?”
“Watch,” urged her companion.
And as they watched they suddenly saw a beam of intense, white light, a miniature searchlight of great brilliance, pierce the darkness skyward. The man Aylesworth was manipulating what they now recognised to be an acetylene signalling apparatus, a cylinder mounted upon a light tripod of aluminium, with a bright reflector behind the gas-jet, and, from the manner that the light began to “wink,” three times in quick succession—the Morse letter “S.”—there was evidently some shutter arrangement upon it.
Slowly the beam turned from north to south, making the Morse “S.” upon the clouds time after time.
Suddenly the light was shut off. For five minutes by Ronald’s watch no flicker was shown. Then, once again, the series of “S’s.” was repeated in a semi-circle from north to south, and back again.
Another five minutes passed in darkness.
Once more the light opened out and commenced to signal the Morse flashes and flares “N. F.,” “N. F.,” “N. F.,” followed by a long beam of light skyward, slowly sweeping in a circle.
Pryor glanced at his watch. It was then exactly midnight. Aylesworth had, no doubt, a rendezvous with someone. His signal could be seen from that point over a radius of fully thirty miles, or even more, for Ronnie, who understood signalling, was well aware that the portable apparatus being used was one of the most intense and reliable type—one that was, indeed, being used by the German army in Flanders.
For the next half-hour the signals were repeated, until, of a sudden, Beryl’s quick ears caught some unusual sound.
“Hark!” she whispered.