The meaning of the message was plain to all on board. The Capella was to proceed to Rendezvous Y, which according to Admiralty instructions was off Yarmouth, Isle of Wight, where a flotilla of small craft was patrolling day and night, as a precautionary measure in the unlikely event of any hostile craft forcing the formidable defences of the western entrance to the Solent.
At eight on the following morning the Taurus arrived on the station, and with the least possible delay the Capella made for the west'ard.
Only one incident marked the run. A few miles from the Royal Sovereign Lightship, the Capella sighted a number of submarines running on the surface. They were on Particular Service, and although opportunities for torpedoing a hostile surface craft were very remote, the submarines were constantly rendering yeoman service by keeping the approaches to the German North Sea ports under close observation. On rare occasions, when a German light-cruiser or destroyer did venture beyond the protection of the mine-fields and guns of the land-batteries, British submarines were not backward in seizing their chance of letting loose "tinfish" against their quarry.
Having arrived off Yarmouth, Captain Syllenger reported himself to the senior officer. He came back beaming. The Capella was to take part in combined sea and land operations for the capture of the German agents, who were supplying petrol to one of the submarines, and also for the capture of the U-boat.
The eventful Friday evening came at last. The Capella, in company with four first-class torpedo-boats, was to be ready at a signal from Hurst to make a dash through the North Channel. A fleet of armed trawlers from the Poole base was to operate farther out to sea, in order to cut off the U-boat's retreat should she be lucky enough to escape the attentions of the Capella and her consorts.
At ten o'clock the east-going tidal stream began to set through the Needles Channel. Half an hour later it ran with a velocity exceeding five knots. The Capella, moving at a rate equal to that of the tide, kept about half a mile from the Isle of Wight shore, with the white, occulting light of the Needles just visible to the north of Cliff End Fort.
It was a perfectly calm night, overcast, but with no wind. A dull rumble, rising and falling in volume, could be heard from the direction of the open sea.
"Breakers on the Shingles—a large bank on the starboard hand of the Needles Channel," explained Barry in answer to the midshipmen's enquiry.
"Then it means that bad weather is approaching," said Ross, who had had plenty of opportunities of observing the phenomenon of "ground swells" on the North Cornish coast. "If it's like this, the U-boat won't be able to make direct communication with the shore."
The appearance of Captain Syllenger on the bridge put an end to conversation. The officers, by the aid of telescopes and binoculars, kept the Hampshire shore under close observation.