"Why, then, the normal pupils of the eyes? Simply because the
criminal put a little atropine, or belladonna, with the morphine.
My tests show absolutely the presence of atropine, Dr. Hanson,"
said Craig, bowing to the physician.

"The best evidence, however, is yet to come. A second box of six
capsules, all intact, was discovered yesterday in the possession
of Henry Vandam. I have analysed the capsules. One contains no
quinine at all--it is all morphine and atropine. It is, without
doubt, precisely similar to the capsule which killed Mrs. Vandam.
Another night or so, and Henry Vandam would have died the same
death."

The old man groaned. Two such exposures had shaken him. He looked
from one of us to another as if not knowing in whom he could
trust. But Kennedy hurried on to his next point.

"Who was it that gave the prescription to Mrs. Vandam originally?
She is dead and cannot tell. The others won't tell, for the
person who gave her that prescription was the person who later
substituted the fatal capsule in place of the harmless. The
original prescription is here. I have been able to discover from
it nothing at all by examining the handwriting. Nor does the
texture of the paper indicate anything to me. But the ink--ah,
the ink.

"Most inks seem very similar, I suppose, but to a person who has
made a study of the chemical composition of ink they are very
different. Ink is composed of iron tannate, which on exposure to
air gives the black of writing. The original pigment--say blue or