And yet, so strange and mysterious a personality was he that not twenty persons in the whole criminal world had ever met him in the flesh.  The tall, good-looking man whom Dorise knew as the White Cavalier was one of four other men who posed in his stead when occasion arose.

Scotland Yard, the Surete in Paris, the Pubblica Sicurezza in Rome, and the Detective Department of the New York police knew, quite naturally, of the existence of the elusive Sparrow, but none of them had been able to trace him.

Why?  Because he was only the brains of the great, widespread criminal organization.  He remained in smug respectability, while others beneath his hand carried out his orders—­they were the servants, well-paid too, and he was the master.

No more widespread nor more wonderful criminal combine had ever been organized than that headed by The Sparrow, the little old man whom Londoners believed to be Cockney, yet Italians believed to be pure-bred Tuscan, while in Paris he was a true Parisian who could speak the argot of the Montmartre without a trace of English accent.

As a politician, as a City man, as a professional man, The Sparrow, whose real name was as obscure as his personality, would have made his mark.  If a lawyer, he would have secured the honour of a knighthood—­or of a baronetcy, and more than probable he would have entered Parliament.

The Sparrow was a philosopher, and a thorough-going Englishman to boot.  Though none knew it, he was able by his unique knowledge of the underworld of Europe to give information—­as he did anonymously to the War Office—­of certain trusted persons who were, at the moment of the outbreak of war, betraying Britain’s secrets.

The Department of Military Operations was, by means of the anonymous information, able to quash a gigantic German plot against us; but they had been unable to discover either the true source of their information or the identity of their informant.

“I’d better be off.  It’s late!” said Mr. Howell, after they had been in close conversation for nearly half an hour.

“Yes; I suppose you must go,” The Sparrow remarked, rising.  “I must get Franklyn back.  He must get to the bottom of this curious affair.  I fell that I am being bamboozled by Benton and Molly Maxwell.  The boy is innocent—­he is their victim,” he added; “but if I can save him, by gad!  I will!  Yet it will be difficult.  There is much trouble ahead, I anticipate, and it is up to us, Howell, to combat it!”

“Perhaps Franklyn can assist us?”

“Perhaps.  I shall not, however, know before he gets back here from his adventures in Hungary.  But I tell you, Howell, I am greatly concerned about the lad.  He has fallen into the hands of a bad crowd—­a very bad crowd indeed.”

TWENTIETH CHAPTER

THE MAN WHO KNEW

Late on Thursday night Dorise and her mother were driving home from Lady Strathbayne’s, in Grosvenor Square, where they had been dining.  It was a bright starlight night, and the myriad lamps of the London traffic flashed past the windows as Dorise sat back in silence.