There were no more stairs to go up.
On each of the floors below there had been a dim light--a jet of gas turned low.

But the fifth floor was in darkness.

Someone had put out the light, either in carelessness or for some special reason.
There were several doors on each side of the passage, but I could not be sure that I had reached the right one until I'd lighted a match.

When I was sure, I knocked, but no answer came.
"He can't be out," I said to myself, cheerfully.

"He's got tired of waiting and dropped asleep, that's all." I knocked again.Silence.And then for a third time, loudly, keeping on until I was sure that, if there were anyone in the room, no matter how sound asleep, I must have waked him.
After all, he had gone out, but perhaps only for a short time.