riend for a moment and then continued: "But how did you know that
Edyth heard a door close immediately after the pistol shot?"

They had just drawn up in front of Hume's, and as Ashton-Kirk got out,
he said:

"If you had only used your eyes as we were going over the place," said
he, "you'd have no occasion to ask that question."

There was a different policeman at the door; but fortunately he knew
the investigator and they were allowed to enter at once. When about
half way up the stairs, Ashton-Kirk said:

"This, I think, is about the place where Miss Vale stopped when she
saw the light-rays moving across the ceiling and wall of the hall. You
get the first glimpse of those from this point. Remain here a moment
and I'll try and reproduce what she heard--with the exception of the
cry."

Pendleton obediently paused upon the stairs; Ashton-Kirk went on up
and disappeared. In a few moments there came a sharp, ringing report,
and Pendleton, dashing up the stairs, saw his friend standing holding
open the showroom door--the one with Hume's name painted upon it.

"It's the bell," said Ashton-Kirk, pointing to the gong at the top of
the door frame. "When I examined it this morning I saw that it was
screwed up too tight, and knew that it would make a sound much like a
pistol shot to ears not accustomed to it."

Pendleton stared in amazement at the simplicity of the thing.

"I see," said he. "While Edyth stood listening on the stairs someone
opened this door!"

"Yes; someone unacquainted with the place. Otherwise he would have
known of the bell."

"But how did you know that Edyth heard a door close?"

"Whoever rang the bell closed the door after him. It has a spring lock
like the street door; and was locked when Miss Vale tried it a few
moments later."

"You say that the ringing of the bell shows the person who rang the
bell to have been unacquainted with the place. I think you must be
wrong here. Spatola is acquainted with the place; he was here at the
time. This is proven by the scream of the frightened cockatoo which
followed the ringing of the bell."

"It was not a cockatoo that made the sound," said Ashton-Kirk. "Give
me a moment and I think I can convince you of that."

The gas in the hall was lighted; the investigator stopped at the foot
of the stairs leading to the fourth floor.

"Persons," he continued, "who secretly enter buildings, as a rule
never trust to the lighting apparatus of the buildings. One r