“Listen, this was how it was done. The valet was in the empty room next door, waiting. The French maid leaves the room. Quick as a flash the chambermaid whips open the drawer, takes out the jewel-case, and, slipping back the bolt, passes it through the door. The valet opens it at his leisure with the duplicate key with which he has provided himself, extracts the necklace, and waits his time. Célestine leaves the room again, and—pst!—in a flash the case is passed back again and replaced in the drawer.
“Madame arrives, the theft is discovered. The chambermaid demands to be searched, with a good deal of righteous indignation, and leaves the room without a stain on her character. The imitation necklace with which they have provided themselves has been concealed in the French girl’s bed that morning by the chambermaid—a master stroke, ça!”
“But what did you go to London for?”
“You remember the card?”
“Certainly. It puzzled me—and puzzles me still. I thought——”
I hesitated delicately, glancing at Mr. Opalsen.
Poirot laughed heartily.
“Une blague! For the benefit of the valet. The card was one with a specially prepared surface—for finger-prints. I went straight to Scotland Yard, asked for our old friend Inspector Japp, and laid the facts before him. As I had suspected, the finger-prints proved to be those of two well-known jewel thieves who have been ‘wanted’ for some time. Japp came down with me, the thieves were arrested, and the necklace was discovered in the valet’s possession. A clever pair, but they failed in method. Have I not told you, Hastings, at least thirty-six times, that without method——”
“At least thirty-six thousand times!” I interrupted. “But where did their ‘method’ break down?”
“Mon ami, it is a good plan to take a place as chambermaid or valet—but you must not shirk your work. They left an empty room undusted; and therefore, when the man put down the jewel-case on the little table near the communicating door, it left a square mark——”