You have lost your gold pencil-case? You must go to the little Belgian. He is too marvellous! Every one goes! Courez!' And they arrive! In flocks, mon ami! With problems of the most foolish!" A bell rang below. "What did I tell you? That is Miss Marvell."

As usual, Poirot was right. After a short interval, the American film star was ushered in, and we rose to our feet.

Mary Marvell was undoubtedly one of the most popular actresses on the screen. She had only lately arrived in England in company with her husband, Gregory B. Rolf, also a film actor. Their marriage had taken place about a year ago in the States and this was their first visit to England. They had been given a great reception. Every one was prepared to go mad over Mary Marvell, her wonderful clothes, her furs, her jewels, above all one jewel, the great diamond which had been nicknamed, to match its owner, "the Western Star." Much, true and untrue, had been written about this famous stone which was reported to be insured for the enormous sum of fifty thousand pounds. All these details passed rapidly through my mind as I joined with Poirot in greeting our fair client. Miss Marvell was small and slender, very fair and girlish-looking, with the wide innocent blue eyes of a child.

Poirot drew forward a chair for her, and she commenced talking at once.

"You will probably think me very foolish, Monsieur Poirot, but Lord Cranshaw was telling me last night how wonderfully you cleared up the mystery of his nephew's death, and I felt that I just must have your advice. I dare say it's only a silly hoax - Gregory says so - but it's just worrying me to death."

She paused for breath. Poirot beamed encouragement.

"Proceed, madame. You comprehend, I am still in the dark."

"It's these letters." Miss Marvell unclasped her handbag, and drew out three envelopes which she handed to Poirot.

The latter scrutinized them closely.

"Cheap paper - the name and address carefully printed. Let us see the inside." He drew out the enclosure.

I had joined him, and was leaning over his shoulder. The writing consisted of a single sentence, carefully printed like the envelope. It ran as follows:

"The great diamond which is the left eye of the god must return whence it came." The second letter was couched in precisely the same terms, but the third was more explicit:

"You have been warned. You have not obeyed. Now the diamond will be taken from you. At the full of the moon, the two diamonds which are the left and right eye of the god shall return. So it is written."

"The first letter I treated as a joke," explained Miss Marvell. "When I got the second, I began to wonder. The third one came yesterday, and it seemed to me that, after all, the matter might be more serious than I had imagined."

"I see they did not come by post, these letters."