found me under the lamp in my study, giving the
distracted young man a narcotic. When his head was nodding, he struggled
once to open his eyes.

"I don't understand--anything--blades of grass--or anything," he
asserted sleepily, as I closed his door.

Exhaustion had brought its childlike petulance, but I knew that
drowsiness would do its work, and that he was now safely stowed away for
at least ten hours. He would not interfere with my plans before noon.

For a few moments that night I sat on the edge of my own bed.

"What if I am right?" I whispered to myself. "What a drama! What a peep
into the unexplored corners of our souls!"

I went to the window. An early milk cart clattered along the
thoroughfare with a figure nodding on its seat. When the mud-spattered
white horse had reached a circle of light shed from the lamp on the
street corner, the figure arose and, looking up at the stars in the
rifts of the sky, pulled off and folded a rubber coat. The storm had
blown away.

"He does a simple little act," I said to myself as I watched the figure
seat itself again. "His thoughts may be as simple. But the consequences
of either! Who can say? Life itself is all on one side of a blue wall!"

* * * * *

Physicians, however, make good detectives. I mention this not to point
out my own case particularly, but merely to call your attention to the
fact that a good surgeon or practitioner has a training in those
qualities of mind which produce a great solver of mysteries. A good
physician must develop the powers of observation. In any physical
disorder, knowing the cause, he must forecast the effect, or with the
evidences of some effect before him, he must deduce the cause. Above all
he must keep his mind from jumping at false conclusions, even though
these conclusions are in line with all his former experiences.
Physicians learn these principles by their mistakes in following clues.
A good diagnostician has in him the material for an immortal police
inspector. I speak modestly, and yet I must say that the next morning
proved that I was not mistaken in these theories.

Before nine o'clock I had arrived at the Marburys'. The banker himself
opened the door.

"Doctor!" he cried, his face drawn out of its mask of eternal shrewdness
and suspicion by a beaming smile, "what can I say? How can we ever show
our gratitude?"

"Not so fast!" I reproved him. "There is danger in too much opt