This last question alone bade fair to confound his utmost ingenuity.
As for what it was, Lanyard was well satisfied that he now held the true focus of this conspiracy, a secret of the first consequence, far too momentous to the designs of England to be entrusted, though couched in the most cryptic cipher ever mind of man devised, even to cables or mails which England herself controlled.
Solely to prevent this communication from reaching America, Lanyard believed, Germany had sown mines broadcast in all the waters which the _Assyrian_ must cross, and had commissioned her U-boats, without fail and at whatever cost, to sink the vessel if by any accident she won safely through the mine-fields.
In the effort to steal this secret, German spies had sailed on the _Assyrian_ knowing well the double risk they ran, of being shot like rats if found out, of being drowned like neutrals if the ship went down through the efforts of their compatriots.
It was the zeal of Potsdam's agents, seeking the bearer of this secret, which had caused the rifling of Miss Brooke's luggage when she fell under suspicion, thanks to her clandestine way of coming aboard; and through the same agency young Thackeray had been all but murdered when suspicion, for whatever reason, shifted to him.
To insure safe transmission of this communication, England had held the _Assyrian_ idle in port, day after day, while her augmented patrols scoured the seas, hunting down ruthlessly every submarine whose periscope dared peer above the surface, and while her trawlers innumerable swept the channels clear of mines.
To prevent its theft, Lieutenant Thackeray had invented the subterfuge of the "wounded" arm, amid whose splints and bandages (Lanyard never doubted) the cylinder had been secreted.
Finally, it was as a special agent, deep in her country's confidence, that this English girl had smuggled herself aboard at the last moment, bringing, no doubt, this very cylinder to be transferred to the keeping of Lieutenant Thackeray or, perhaps, another confrère, should she find reason to think herself suspected, her trust endangered.
Nothing strange in that; women had served their countries in such capacities before; the secret archives of European chancellories are replete with their records. Lanyard himself remembered many such women, brilliant mondaines from many lands domiciled in that Paris of the so-dead yesterday to serve by stealth their respective governments; but never, it was true, a woman of the caste of Cecelia Brooke; unless, indeed, this were an actress of surpassing talent, gifted to hoodwink the most skeptical and least susceptible of men.