"All ready, sir," repeated Spanner. "The whole of the petrol-tanks are filled."
The officers went on deck. Men were busily engaged in easing off the steel hawsers by which the destroyer was secured to the jetty. The signal for "permission to part company" was fluttering from her mast. head. Aft the awnings had been unrigged, and were being handed down for stowage below.
Presently a hoist of signal flags was run up to the yard-arm of the semaphore tower.
"Permission, sir," reported the signalman of the destroyer, laconically.
The engine-room telegraph bell clanged, the water churned under the destroyer's stern as her propellers began to revolve. The last "spring" that held her to the shore was cast off, and the Frome started on her mission of investigation.
Three hours later she was off Beachy Head, but, although keeping in touch with Portsmouth Dockyard by means of wireless, and communicating with every vessel that passed up and down that busy highway—the English Channel—the Impregnable seemed to have vanished, leaving no trace behind her.
"Wreckage, sir," reported the look-out.
Heading towards the spot, and ordering the propellers to be stopped, Drake got his glasses to bear upon the spot. There were a number of oars, some gratings, a large hatch, and a yellow-painted lifebuoy, bearing the name "Hekla, Rotterdam."
"That's the name of one of the tugs, sir," said Fielding. "So the master of the Wontwash has not been telling a mere fairy tale."
"That's so," assented the lieutenant-commander. "I suppose we ought to secure that lifebuoy as evidence. Stand by with a boathook there."