Cavendish sat bolt upright in the chair. Now he was beginning to grasp the drift of things. Hitherto, he had been groping blindly, trying to piece together the baffling questions which the Commander had put to him, in a vain endeavour to discover the nature of the hazardous duty hinted at.
He knew the Cynesephon. She was one of the "P" boats that in 1918 had been converted into a "Q" ship and altered to resemble a South American freighter. She was supposed to be the last word in mystery ships, but an opportunity to use her never arrived, owing to the Armistice.
For certain reasons she had not been scrapped. She was now lying in one of the basins at Portsmouth Dockyard, snugly moored between two battleships of the Thunderer class, which were permanently out of commission.
And now the Cynesephon was to be rescued from the scrap heap and reconditioned—why?
Putting two and two together—the commissioning of the Cynesephon and the Commander's inquiries about Cavendish's service on the South American station—the Sub made a shrewd guess.
For several days there had been reports of British ships bound to and from Brazilian and Argentine ports being overdue. Several of them had been posted at Lloyd's as missing. At first, the general public hardly noticed the information, and until the Press gave prominence to the matter, few people outside the shipping circles had any idea of the persistent increase of the list of vessels overdue.
Then sprang up the usual crop of rumours—a pirate in the South Atlantic providing the favourite topic. Vessels of all nationalities had cleared South American ports and had made their various destinations. None of the masters had reported falling in with a suspicious craft; but it was an ominous fact that, without exception, the overdue vessels had sailed under the Red Ensign.
A question was raised in the House concerning the mysterious disappearance of so many ships, to which the First Lord made a reply that the Admiralty were considering the matter, but did not feel justified in sending H.M. ships, which were urgently required elsewhere, to investigate.
That reply was a "blind". Already orders had been issued for the secret commissioning of the Cynesephon and the dispatch of the light cruiser Basilikon and the 35-knot destroyers Messines and Armentières to the West Indies.
"It is in connection with the missing merchantmen, sir?" asked Cavendish.