Mysterious Mr. Sabin by E. Phillips Oppenheim

The Countess of Deringham might be excused for considering herself the most unfortunate woman in England. In a single week she had passed from the position of one of the most brilliant leaders of English society to be the keeper of a recluse, whose sanity was at least doubtful. Her husband, Admiral the Earl of Deringham, had been a man of iron nerve and constitution, with a splendid reputation, and undoubtedly a fine seaman. The horror of a single day had broken up his life. He had been the awe-stricken witness of a great naval catastrophe, in which many of his oldest friends and companions had gone to the bottom of the sea before his eyes, together with nearly a thousand British seamen. The responsibility for the disaster lay chiefly from those who had perished in it, yet some small share of the blame was fastened upon the onlookers, and he himself, as admiral in command, had not altogether escaped.

From the moment when they had led him down from the bridge of his flagship, grey and fainting, he had been a changed man. He had never recovered from the shock. He retired from active service at once, under a singular and marvellously persistent delusion. Briefly he believed, or professed to believe, that half the British fleet had perished, and that the country was at the mercy of the first great Power who cared to send her warships up the Thames. It was a question whether he was really insane; on any ordinary topic his views were the views of a rational man, but the task which he proceeded to set himself was so absorbing that any other subject seemed scarcely to come within the horizon of his comprehension. He imagined himself selected by no less a person than the Secretary for War, to devote the rest of his life to the accomplishment of a certain undertaking!