“Then they are the marks of Miss Chevenix-Gore. Ah, yes, I remember she mentioned having been out in the garden yesterday evening.”
He led the way back round the house.
“Are we still sleuthing?” asked Susan.
“But certainly. We will go now to Sir Gervase’s study.”
He led the way. Susan Cardwell followed him.
The door still hung in a melancholy fashion. Inside, the room was as it had been last night. Poirot pulled the curtains and admitted the daylight.
He stood looking out at the border a minute or two, then he said:
“You have not, I presume, mademoiselle, much acquaintance with burglars?”
Susan Cardwell shook her red head regretfully.
“I’m afraid not, M. Poirot.”
“The chief constable, he, too, has not had the advantages of a friendly relationship with them. His connection with the criminal clases has always been strictly official. With me that is not so. I had a very pleasant chat with a burglar once. He told me an interesting thing about french windows—a trick that could sometimes be employed if the fastening was sufficiently loose.”
He turned the handle of the left-hand window as he spoke, the middle shaft came up out of the hole in the ground, and Poirot was able to pull the two doors of the window towards him. Having opened them wide, he closed them again—closed them without turning the handle, so as not to send the shaft down into its socket. He let go of the handle, waited a moment, then struck a quick, jarring blow high up on the centre of the shaft. The jar of the blow sent the shaft down into the socket in the ground—the handle turned of its own accord.
“You see, mademoiselle?”
“I think I do.”
Susan had gone rather pale.
“The window is now closed. It is impossible to enter a room when the window is closed, but it is possible to leave a room, pull the doors to from outside, then hit it as I did, and the bolt goes down into the ground, turning the handle. The window then is firmly closed, and anyone looking at it would say it had been closed from the inside.”
“Is that”—Susan’s voice shook a little—“is that what happened last night?”
“I think so, yes, mademoiselle.”
Susan said violently:
“I don’t believe a word of it.”
Poirot did not answer. He walked over to the mantelpiece. He wheeled sharply round.
“Mademoiselle, I have need of you as a witness. I have already one witness, Mr. Trent. He saw me find this tiny sliver of looking glass last night. I spoke of it to him. I left it where it was for the police. I even told the chief constable that a valuable clue was the broken mirror. But he did not avail himself of my hint. Now you are a witness that I place this sliver of looking glass (to which, remember, I have already called Mr. Trent’s attention) into a little envelope—so.” He suited the action to the word. “And I write on it—so—and seal it up. You are a witness, mademoiselle?”
“Yes—but—but I don’t know what it means.”
Poirot walked over to the other side of the room. He stood in front of the desk and stared at the shattered mirror on the wall in front of him.
“I will tell you what it means, mademoiselle. If you had been standing here last night, looking into this mirror, you could have seen in it murder being committed. . . .”
Twelve
I
For once in her life Ruth Chevenix-Gore—now Ruth Lake—came down to breakfast in good time. Hercule Poirot was in the hall and drew her aside before she went into the dining room.
“I have a question to ask you, madame.”
“Yes?”