“Could you find it convenient,” Francis asked, with icy politeness, “to return to your own table, stealthily or not, as you choose?”

The newcomer showed no signs of moving.

“In after years,” he declared, “you would be the first to regret the fact if I did so.  This is a momentous meeting.  It gives me an opportunity of expressing my deep gratitude to you, Mr. Ledsam, for the wonderful evidence you tendered at the inquest upon the body of my son-in-law, Oliver Hilditch.”

Francis turned in his place and looked steadily at this unsought-for companion, learning nothing, however, from the half-mocking smile and imperturbable expression.

“Your son-in-law?” he repeated.  “Do you mean to say that you are the father of—­of Oliver Hilditch’s wife?”

“Widow,” the other corrected gently.  “I have that honour.  You will understand, therefore, that I feel myself on this, the first opportunity, compelled to tender my sincere thanks for evidence so chivalrously offered, so flawlessly truthful.”

Francis was a man accustomed to self-control, but he clenched his hands so that his finger nails dug into his flesh.  He was filled with an insane and unreasoning resentment against this man whose words were biting into his conscience.  Nevertheless, he kept his tone level.

“I do not desire your gratitude,” he said, “nor, if you will permit me to say so, your further acquaintance.”

The stranger shook his head regretfully.

“You are wrong,” he protested.  “We were bound, in any case, to know one another.  Shall I tell you why?  You have just declared yourself anxious to set your heel upon the criminals of the world.  I have the distinction of being perhaps the most famous patron of that maligned class now living—­and my neck is at your service.”

“You appear to me,” Francis said suavely, “to be a buffoon.”

It might have been fancy, but Francis could have sworn that he saw the glitter of a sovereign malevolence in the other’s dark eyes.  If so, it was but a passing weakness, for a moment later the half good-natured, half cynical smile was back again upon the man’s lips.

“If so, I am at least a buffoon of parts,” was the prompt rejoinder.  “I will, if you choose, prove myself.”

There was a moment’s silence.  Wilmore was leaning forward in his place, studying the newcomer earnestly.  An impatient invective was somehow stifled upon Francis’ lips.

“Within a few yards of this place, sometime before the closing hour to-night,” the intruder continued, earnestly yet with a curious absence of any human quality in his hard tone, “there will be a disturbance, and probably what you would call a crime will be committed.  Will you use your vaunted gifts to hunt down the desperate criminal, and, in your own picturesque phraseology, set your heel upon his neck?  Success may bring you fame, and the trail may lead—­well, who knows where?”