In the meantime Bernard Boyne had been startled by the ringing of the bell, yet in the full knowledge that Mrs. Felmore could hear nothing. That secret alarm had, as a matter of fact, been installed with his own hands about two months before, with its switch concealed in the upstairs room.
On hearing it, he instantly flung off his white cloak and dashed headlong down the stairs.
In the hall, however, he halted and burst out laughing.
"Fool you are, Bernard!" he exclaimed aloud to himself. "Yes, you are getting more nervous every day!"
The reason of this was because close to the front door sat Mrs. Felmore's black cat, waiting to be let out for the night.
"Ah, pussy!" he exclaimed. "So it is you who ran silently down the stairs and set off the gong, eh?"
And, opening the door, he let out the cat, saying:
"Out you go, Jimmy, and don't do it again."
Then he reascended the stairs to the locked room, perfectly satisfied with the solution of what a few moments before had caused him very considerable alarm.
No intruder would be tolerated in that dingy house—the house of great mystery.