But one day—it was exactly a month from the time when Tressidar first set foot in the fortress of Sylt—the long-expected attack took place.
Through the brilliant sunlit air six British seaplanes, looking little larger than may-flies, headed straight for the island. Well in the offing lay a parent ship for seaplanes, four light cruisers, and a swarm of destroyers; while still further to the westward the giant battle-cruisers kept in touch with their smaller consorts, ready to swoop down upon the German warships should the latter be tempted to join issue with the audacious British.
Tressidar and Fuller were alone in the common room. Owing to a trumped-up charge of a breach of discipline they had been prevented from joining the rest of their comrades in misfortune for the daily outdoor recreation.
A tremendous outburst of shell from the light quick-firers brought the chums to the barred window. Although they had had plenty of disappointment over the false alarms, they never neglected the opportunity of making for a place of observation when the anti-aircraft guns opened fire. For days they had waited for "something to turn up," and now their optimistic patience was about to be rewarded.
"Five of them, by Jove!" exclaimed Fuller. "No, six. They'll play the deuce with the Huns."
"And possibly with us," thought the sub., but nevertheless his nerves were a-tingle and his hopes centred upon the main idea that the raid would be of brilliant military importance. Personal safety was a negligible quantity.
All around the biplanes were white, mushroomed clouds of smoke from the bursting shrapnel. It seemed as if nothing in the vicinity could escape the concentrated fire from the German guns, yet serenely the seaplanes held on their course, tilting slightly under the violent disturbance of the air.
With their faces pressed against the iron bars of the window the two young officers watched the progress of the aircraft until they were so immediately overhead that the masonry impeded their outlook. The last they saw of the daring raiders was that they were volplaning rapidly.
"Now stand by!" whispered Fuller tersely. "In another few seconds you'll hear the plums drop."
The anti-aircraft guns redoubled their furious fire. The whole building trembled under the reverberation of the deafening reports.