"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.