No second glance was needed, as soon as the Professor’s attention had been called to this appearance, to ensure the riveting of his attention on it.  Nor was much examination necessary to convince him that he had now, in truth, discovered the cause and the means of death.

The slight mark in question was, in fact, the trace of a wound inflicted by a very fine needle, which had pierced the heart, and, having caused immediate death, had been left in the wound, ingeniously hidden by means which it needed a second look to discover.  The effect of this discovery on the Professor was singular.  He seemed taken aback by it, and, one would have said, alarmed at it, in a manner which it seemed difficult for Signor Fortini to account for.  “What is it astonishes you so, Signor Professore,” said he; “surely you were prepared to find that a murder had been done?  I never had any doubt of it; and why not in that way as well as another?  And a very ingenious mode of inflicting death in a quiet way it seems to be.”

“Yes, indeed.  The fact is that I was struck by—­”

The Professor broke off speaking suddenly with a start; and darted a quick alarmed glance at the face of Signor Fortini, who did not fail to remark it, and to be much puzzled by the Professor’s manner.

The latter, while he had been speaking, had stooped to examine the minute trace of the wound closely, and had put his finger on the spot; and it was on doing so that he had interrupted himself, and shown renewed symptoms of surprise and dismay.  What this closer examination had shown him was the fact that an infinitesimally small portion of white wax had been very neatly and carefully introduced into the orifice of the wound, in such a manner as to prevent all effusion of blood, and almost to escape the observation of the naked eye.

“Why, one would say you were a novice at this sort of thing, Tomosarchi, you seem so much affected by it,” said the lawyer; “what is it that moves you so?  Why, you are as pale, man, as if you were bringing to light a crime of your own instead of somebody else’s.”

“Ah! not that exactly.  No, but it is a very singular thing.  One would say that this death must have been caused by some one who had some little knowledge of anatomy, or, at least, had been put up to the trick by some one else who possessed such knowledge,” said the Professor, recovering himself with an effort.

“And that is what our friend the Marchesino Ludovico is most assuredly innocent of.  I take note of your remark, Signor Professore,” said the lawyer.

“But one would think, that all the other persons on whom it is possible that suspicion might rest, must be equally void of any such knowledge,” returned Tomosarchi.