“Or—what——” said Maida.

A remnant of common sense saved me, I think, from stark terror. I took a firmer hold on my imagination.

“Nonsense,” I spoke decidedly but still, for some reason, in a whisper. “There are no such things as—as—— I mean to say, the shadow you saw was either an optical illusion or a living, breathing person.”

“Certainly,” agreed Maida, adding inconsistently: “I don’t see how a living person could have got past us, through this long corridor without one of us seeing him—it.”

My eyes fell on the south door near at hand; the tiny panes of glass winked blackly at me as I crossed to it, grasped the brass latch and pulled. The door swung slowly open, letting in a current of cold, mist-laden air.

“There, you see?” I said to Maida. “Only a real, material thing needs a door to go through.”

Maida was looking at me strangely.

“I don’t see that that helps matters any,” she said. “I locked that door myself, to-night. It just proves that someone was actually here. That the murderer is still about the hospital.”

“Not necessarily,” I said, though my heart was pounding in my throat. “You are sure you locked it?”

“Positive.”