to see what that man has done to it."

"What do you suspect?"

She shrugged her graceful shoulders half imperceptibly.

"How should I know? Anything!"

I gazed at the needle closely. "What made you distrust it?" I inquired
at last, still eyeing it.

She opened a drawer, and took out several others. "See here," she said,
handing me one; "THESE are the needles I keep in antiseptic wool--the
needles with which I always supply the Professor. You observe their
shape--the common surgical patterns. Now, look at THIS needle, with
which the Professor was just going to prick my finger! You can see for
yourself at once it is of bluer steel and of a different manufacture."

"That is quite true," I answered, examining it with my pocket lens,
which I always carry. "I see the difference. But how did you detect it?"

"From his face, partly; but partly, too, from the needle itself. I had
my suspicions, and I was watching him closely. Just as he raised the
thing in his hand, half concealing it, so, and showing only the point,
I caught the blue gleam of the steel as the light glanced off it. It was
not the kind I knew. Then I withdrew my hand at once, feeling sure he
meant mischief."

"That was wonderfully quick of you!"

"Quick? Well, yes. Thank Heaven, my mind works fast; my perceptions are
rapid. Otherwise--" she looked grave. "One second more, and it would
have been too late. The man might have killed me."

"You think it is poisoned, then?"

Hilda shook her head with confident dissent. "Poisoned? Oh, no. He
is wiser now. Fifteen years ago, he used poison. But science has made
gigantic strides since then. He would not needlessly expose himself
to-day to the risks of the poisoner."

"Fifteen years ago he used poison?"

She nodded, with the air of one who knows. "I am not speaking at
random," she answered. "I say what I know. Some day I will explain. For
the present, it is enough to tell you I know it."

"And what do you suspect now?" I asked, the weird sense of her strange
power deepening on me every second.

She held up the incriminated needle again.

"Do you see this groove?" she asked, pointing to it with the tip of
another.

I examined it once more at the light with the lens. A longitudinal
groove, apparently ground into one side of the needle, lengthwise, by
means of a small grinding-stone and emery powder, ran for a quarter of
an inch above the point. This groove seemed to me to have been produced
by an amate