I assured her that I was well aware that in the struggle for house-room the baser side of human nature frequently triumphed over the higher, and that the well-known rule of dog eat dog always applied.

"So we went up and, would you believe it, the flat wasn't let at all. We were shown over it by the maid, and then we saw the mistress, and the thing was settled then and there. Immediate possession and fifty pounds for the furniture. We signed the agreement next day, and we are to move in tomorrow!" Mrs Robinson paused triumphantly.

"And what about Mrs Ferguson?" asked Parker. "Let's have your deductions, Hastings."

"'Obvious, my dear Watson,'" I quoted lightly. "She went to the wrong flat."

"Oh, Captain Hastings, how clever of you!" cried Mrs Robinson admiringly. I rather wished Poirot had been there. Some times I have the feeling that he rather underestimates my capabilities.

The whole thing was rather amusing, and I propounded the thing as a mock problem to Poirot on the following morning. He seemed interested, and questioned me rather narrowly as to the rents of flats in various localities.

"A curious story," he said thoughtfully. "Excuse me, Hastings, I must take a short stroll." When he returned, about an hour later, his eyes were gleaming with a peculiar excitement. He laid his stick on the table, and brushed the nap of his hat with his usual tender care before he spoke.

"It is as well, mon ami, that we have no affairs of moment on hand. We can devote ourselves wholly to the present investigation."

"What investigation are you talking about?"

"The remarkable cheapness of your friend's, Mrs Robinson's, new flat."

"Poirot, you are not serious!"

"I am most serious. Figure to yourself, my friend, that the real rent of those flats is £350. I have just ascertained that from the landlord's agents. And yet this particular flat is being sublet at eighty pounds! Why?"

"There must be something wrong with it. Perhaps it is haunted, as Mrs Robinson suggested." Poirot shook his head in a dissatisfied manner.

"Then again how curious it is that her friend tells her the flat is let, and, when she goes up, behold, it is not so at all!"

"But surely you agree with me that the other woman must have gone to the wrong flat. That is the only possible solution."

"You may or may not be right on that point, Hastings. The fact still remains that numerous other applicants were sent to see it, and yet, in spite of its remarkable cheapness, it was still in the market when Mrs Robinson arrived."

"That shows that there must be something wrong about it."

"Mrs Robinson did not seem to notice anything amiss. Very curious, is it not? Did she impress you as being a truthful woman, Hastings?"

"She was a delightful creature!"

"Évidemment! since she renders you incapable of replying to my question. Describe her to me, then."

"Well, she's tall and fair; her hair's really a beautiful shade of auburn -"