She inserted the key and uttered a note of exclamation, for the door yielded under her pressure and opened.
"It is unlocked," she said.

"I am sure I fastened it." Tarling put his lamp upon the lock and made a little grimace.

The catch had been wedged back into the lock so that it could not spring out again.
"How long were you in the house ?" he asked quickly.
"Only a few minutes," said the girl.

"I went in just to tell mother, and I came out immediately." "Did you close the door behind you when you went in ?" The girl thought a moment.
"Perhaps I didn't," she said.

"No, of course not--I didn't come back this way; mother let me out by the front door." Tarling put his light into the hall and saw the carpeted stairs half-a-dozen feet away.