"It's supernatural!" he muttered—all that was Celtic in his blood recoiling from the omen. "Nothing human can reach that window!" "S-sh!" from Smith. "Don't stir."
The tapping was repeated.
Smith softly crossed the room. My heart was beating painfully. He threw open the window. Further inaction was impossible. I joined him; and we looked out into the empty air.
"Don't come too near, Petrie!" he warned over his shoulder.
One on either side of the open window, we stood and looked down at the moving Embankment lights, at the glitter of the Thames, at the silhouetted buildings on the farther bank, with the Shot Tower starting above them all.
Three taps sounded on the panes above us.
In all my dealings with Dr. Fu-Manchu I had had to face nothing so uncanny as this. What Burmese ghoul had he loosed? Was it outside, in the air? Was it actually in the room?
"Don't let me go, Petrie!" whispered Smith suddenly. "Get a tight hold on me!"
That was the last straw; for I thought that some dreadful fascination was impelling my friend to hurl himself out! Wildly I threw my arms about him, and Guthrie leaped forward to help.
Smith leaned from the window and looked up.