click

At that instant there was a sharp click, the jangling of metal, and Sherlock Holmes sprang to his feet again.

Still kneeling upon the floor he bent forward and threw all his weight and strength upon some lever, with the result that there came a long, whirling, grinding noise, ending once more in a powerful click.

“Hist!” cried Holmes, and I heard the sharp click of a cocking pistol.

We heard the servant pass along the hall, and the sharp click of the latch as she opened it.