"I was called downstairs to see Mr. Musard. An unused outside door which is generally kept locked was discovered unlocked by the butler before the murder was committed. As the door opens on a staircase leading to the left wing, Mr. Musard thought the butler's discovery had some bearing on the crime." "He thought the murderer may have entered the house that way? Such a theory would suggest that one of the servants is implicated." "Yes; but I do not agree with Mr. Musard." "What is your own opinion?" "I think the key must have been left in the door by one of the servants--perhaps some days ago. The fact that the butler locked the door when he found it unfastened did not prevent the murder being committed, or the murderer escaping afterwards." "The murderer may have entered by the door before the butler discovered that it had been unlocked, and then concealed himself inside the house awaiting an opportunity to commit the crime." "In that case, he would have tried to escape the same way, but it is quite certain that he did not do so. Mr. Musard says that the staircase was the first place to be searched when the guests rushed upstairs. If the murderer had gone that way he would have found the door at the bottom locked, and the key removed, and he must have been caught before he could get back upstairs." "There's something in that," said Merrington. "But how do you account for the door being unlocked in the first instance?" "The servants know where the key is kept. One of the maids may have taken it to steal out of the house that way to keep an appointment with a sweetheart, and forgotten all about it when she returned. The back staircase and entrance are never used by the members of the household, and the key, which was inside the door, may have been there for days without being noticed. Tufnell admits that it was only by chance he tried the door yesterday. He had not tried it for weeks before." "I'll have a look at this door later. And now, we had better get to work. We have got to catch this murderer pretty quickly, or the press and the public will be up in arms. He's had too long a start already. You must make up your mind for considerable public indignation about that, Caldew." "I do not see how I can be held responsible for the murderer getting away," said Caldew, in an aggrieved tone. "He had his start before I arrived. I did everything that I could. I searched the house inside and out, and Sergeant Lumbe has been scouring the country-side since daybreak looking for suspicious characters."