he little
tube. Here it is. But I urge you to use it with extreme caution. When
you break the glass be certain that none of the jelly inside touches
your fingers. If it does, wash them instantly in carbolic. It is
highly contagious."

De Gex gave vent to a queer laugh of satisfaction, as, no doubt, he
took the mysterious glass tube in his hand.

"I am not yet certain whether to try the experiment--or not," he
remarked with hesitation.

"It is, to say the least, a highly dangerous one."

"You mean dangerous from the point of view of discovery--eh?"

"No, not at all. Your act cannot be discovered, but it may be
dangerous for yourself and those about you--highly dangerous. I have
obeyed your orders, signore, as I always do, and I have brought it.
But my suggestion is that you should not break that tube and disperse
its contents."

"You seem to be growing unusually apprehensive, my dear Moroni. The
appearance in Florence of this young electrical engineer seems to have
quite upset you!" he laughed harshly. I could hear every word.

"I confess his presence here has not inspired me with confidence. We
do not know the extent of his knowledge, or what he has discovered,"
replied the doctor. "If he establishes one fact--you know to what I
refer--then he will become a very grave menace to us both."

"But surely he won't dare to reveal anything for his own sake. That is
why I made the bribe a substantial one."

"If he established that one fact to which I have referred, then it
would be quite within the bounds of possibility that he might face the
music, and lay bare the whole facts of the mystery of Stretton
Street," Moroni remarked in a rather lower tone. "At present I think
he will keep a still tongue."

"Then one thing is quite plain," said the millionaire. "He must not be
allowed to prosecute his inquiries any further. And it is for you,
Moroni, to rid us of this ever-growing menace. If he is allowed to go
on, then we shall one day awake to find our secret revealed."

"I quite agree. But how shall we act?"

"Ah! I leave that to you," replied De Gex. "You have many ways and
means within your power. He is a patient of yours," he added grimly.

"Yes. But I happen to know that he is sufficiently wide awake not to
take any of my mixtures."

"Ah! Then he suspects you! You must act with greatest caution, Moroni.
Act as you will, but we must, at all costs, get rid of this fellow."

"I suggested that after the affair