door locked till I come back."

With those parting directions he hurried out of the house.

"What _can_ he mean?" said Mr. Engelman, leading the way out of the
bedchamber.

The elder doctor left in charge heard the words, and answered them,
addressing himself, not to Mr. Engelman, but to me. He caught me by the
arm, as I was leaving the room in my turn.

"Poison!" the doctor whispered in my ear. "Keep it a secret; that's what
he means."

I ran to my own bedchamber and bolted myself in. At that one word,
"Poison," the atrocious suggestion of Frau Meyer, when she had referred
to Doctor Fontaine's lost medicine-chest, instantly associated itself in
my memory with Madame Fontaine's suspicious intrusion into Mr. Keller's
room. Good God! had I not surprised her standing close by the table on
which the night-drink was set? and had I not heard Doctor Dormann say,
"That's unlucky," when he was told that the barley-water had been all
drunk by the patient, and the jug and glass washed as usual? For the
first few moments, I really think I must have been beside myself, so
completely was I overpowered by the horror of my own suspicions. I had
just sense enough to keep out of Mr. Engelman's way until I felt my mind
restored in some degree to its customary balance.

Recovering the power of thinking connectedly, I began to feel ashamed of
the panic which had seized on me.