a hideous mistake in arresting her.
Detective Caldew refused to admit the possibility of mistake, but Phil
shuts his eyes to everything that tells against the girl, including her
mother's unpleasant past."

"Did Miss Heredith know anything of her housekeeper's past?"

"No. Mrs. Rath, as she calls herself, came to Heredith many years ago,
took a small cottage, and tried to support her daughter and herself by
giving lessons in music and French. She would have starved if it had not
been for Miss Heredith, who helped her and her little girl, tried to get
the mother some pupils, and finally took her into the moat-house as
housekeeper. Mrs. Rath disappeared from the place after her daughter's
arrest, when the police had decided that it was not necessary to detain
her, leaving a note behind her for Miss Heredith to say that she
couldn't face her after all that had happened."

Colwyn did not speak immediately. He was examining the row of upper
windows which looked down on the garden in which they were standing.

"Is that the window of the room in which Mrs. Heredith was murdered?" he
asked, pointing to the first one.

"Yes. It is high for a first-floor window, but there is a fall in the
ground on this side of the house."

Colwyn tested the strength of the Virginia creeper which grew up the
wall almost to the window, and then bent down to examine the grass and
earth underneath.

"Caldew thought at first that the murderer escaped from the window, but
Merrington did not agree with him," said Musard.

If the remark was intended to extract an expression of opinion from
Colwyn it failed in effect, for he remained silent. He had regained his
feet, and was looking up at the window again.

"Where is the door which opens on the back staircase of this wing?" he
said, at length.

"At the extreme end. You cannot see it from here. It opens on the back
of the house."

"According to the newspaper reports of the case, the door is always kept
locked. Is that correct?"

"As a general rule it is. But it was found unlocked before dinner on the
night the murder was committed."

"I was not informed of this before."

"Phil was not aware of it, and Detective Caldew attached so little
importance to it when I told him after the murder that I should not have
thought it worth mentioning if you had not asked me. Caldew's point of
view was that the door had been left unlocked, accidentally, by one of
the servants, which is quite possible.