om to search for it, he was interrupted by a
low tap at the door. He walked across and opened it. Tufnell stood
outside, grave and composed.

"Mr. Musard would like to see you in the library," he said.

His tone was even and almost deferential, but the detective's watchful
eyes intercepted a fleeting glance cast by the butler over his shoulder
in the direction of the still figure on the bed.

"Very well, I will see him," said the detective.

"I will take you to him, if you will come with me." The butler preceded
him along the passage with noiseless step, and Caldew followed him, deep
in thought.

The butler escorted him to the library, and entered after him. Musard
was in the room alone, standing by the fireplace, smoking a cigar. He
looked up as Caldew entered.

"I have just learnt something which I think you ought to know," he said.
"The information comes from Tufnell. He tells me that while he was going
around the house this afternoon he found the outside door of the back
staircase unlocked."

"Do you mean the door at the bottom of the staircase in the left wing?"
asked Caldew.

"Precisely."

"I understood from Miss Heredith that this door was always kept locked."

"So it is, as a rule. It was only by chance that the butler discovered
this evening that it had been unlocked. You had better explain to the
detective, Tufnell, how you came to find it unfastened."

"I was going round by the back of the house this evening," said the
butler, coming forward. "As I passed the door I tried the handle. To my
surprise it yielded. I opened the door, and found that the key was in
the keyhole, on the other side. I locked the door, and took the key
away."

"What time was this?" inquired Caldew.

"A little before six--perhaps a quarter of an hour."

"Is it your custom to try this door every night?"

"Oh, no, it is not necessary. The door is always kept locked, and the
key hangs with a bunch of other unused keys in a small room near the
housekeeper's apartments, where a number of odds and ends are kept."

"When was the last time you tried the door?"

The butler considered for a moment.

"I cannot rightly say," he said at length. "The door is never used, and
I rarely think of it."

"Then, for all you know to the contrary, the key may have been in the
door for days, or weeks past."

"Why, yes, it is possible, now that you come to mention it," said the
butler, with an air of surprise, as though he had not previo