Pendleton gazed with sober eyes into the speaker’s face for a moment.  Then he said: 

“Let us get the cab; if you are to go over Hume’s rooms before dark, you haven’t any too much time.”

At the next corner they signaled a taxicab, and in a short time they were set down in Christie Place.  Paulson, the policeman, was standing guard.

“How are you?” he greeted them affably.

“Been here all day?” asked Ashton-Kirk.

“Oh, no.  Just come on.  I’m the third shift since I saw you last.”

“Nobody has been permitted to go upstairs, I presume?”

“Only the coroner’s man, who came for the body.  And they touched nothing but the body.  Our orders were strong on that.”

“Has anything been heard as the result of the post-mortem?”

“It showed that Hume was in bad shape from too much drink.  Then he had a hard knock on the head, and the wound in his chest.”

“But there was no sign of a bullet wound?”

“No,” said Paulson, surprised.  “Nothing like that.”

“Just a moment,” said the investigator to Pendleton.  He crossed the street, walked along for a few paces, then paused at the curb and looked back toward Hume’s doorway.  Then he returned with quick steps and an alert look in his eyes.

“Now we’ll go upstairs,” he said.

But before doing so he stopped and examined the lock of the street door closely; then he mounted the stairs slowly, his glances seeming to take in everything.  At the top he paused, his head bent, apparently in deep thought.  Then he lifted it suddenly, and laughed exultantly.

“That’s it,” he said, “I’m quite sure that is it.”

“I wouldn’t doubt your word for an instant,” said Pendleton, in something like his old voice.  “Whatever it is, I’m quite sure it is if you say so.”

The policeman on guard in the hall examined them carefully.

“All right,” said he, after they had explained and he had verified it by calling to his mate at the street door.  “Go right to work, gents.  I’m here to see that nobody gets in from above by way of the scuttle, and I guess I won’t be in the way.”

There were three gas branches at intervals along the length of the dim hall, each with a cluster of four jets.  Ashton-Kirk lighted all three of these and began making a careful examination of the passage.  Along toward the rear was a stairway leading to the floor above.  Next this was a small room in which there was a water tap.  At the extreme end of the hall was a window with a green shade drawn to the bottom.

Ashton-Kirk regarded this for a moment intently.  Then he reached up and turned off the gas at the branch nearest the window.  Daylight could now be seen through the blind; the investigator pointed and said: 

“This shows us something.  About six inches of the bottom of the blind is of a decidedly lighter color than the remainder.  This is caused by exposure to the light and indicates that this blind has seldom been drawn in daylight as it is now.”