If a foe was there with the revolver he was quite likely to hold it levelled at the intruder, because of which Jack, when he burst into the room, held his own weapon pointed, so as to prevent any enemy from "getting the drop" on him.
For one moment the young man believed it was all a mistake and that, despite the precaution taken upon leaving the house, he had not extinguished the lamp, whose wick had recovered its vigor, but the suspicion was hardly formed when he knew there was no foundation for it.

In the first place no lamp ever acts that way, and, the front door having been closed, could not open of itself.

More convincing than all was the fact that Mary Marlowe's revolver, which had brought him back, was missing.
Diagonally across the dining-room from where Jack Everson stood was the door leading to the rear of the house.

This was open for three or four inches, and while searching the apartment with all the keenness of his powerful vision, he distinctly saw it move.

The distance was no more than an inch, but he was not mistaken, and knew it had been drawn that much nearer shut.