On one particular evening in early June, he arrived about half-past eight and settled down to a comfortable discussion on the cheery topic of the prevalence of arsenical poisoning in crimes. It must have been about a quarter of an hour later when the door of our sitting-room flew open, and a distracted female precipitated herself into the room.

"Oh, doctor, you're wanted! Such a terrible voice. It gave me a turn, it did indeed." I recognized in our new visitor Dr Hawker's housekeeper, Miss Rider. The doctor was a bachelor, and lived in a gloomy old house a few streets away. The usually placid Miss Rider was now in a state bordering on incoherence.

"What terrible voice? Who is it, and what's the trouble?"

"It was the telephone, doctor. I answered it - and a voice spoke. 'Help,' it said. 'Doctor - help. They've killed me!' Then it sort of trailed away. 'Who's speaking?' I said. 'Who's speaking?' Then I got a reply, just a whisper, it seemed, 'Foscatine' - something like that - 'Regent's Court.'" The doctor uttered an exclamation.

"Court Foscatini. He has a flat in Regent's Court. I must go at once. What can have happened?"

"A patient of yours?" asked Poirot.

"I attended him for some slight ailment a few weeks ago. An Italian, but he speaks English perfectly. Well, I must wish you good night, Monsieur Poirot, unless -" He hesitated.

"I perceive the thought in your mind," said Poirot, smiling. "I shall be delighted to accompany you. Hastings, run down and get hold of a taxi."

Taxis always make themselves sought for when one is particularly pressed for time, but I captured one at last, and we were soon bowling along in the direction of Regent's Park. Regent's Court was a new block of flats, situated just off St John's Wood Road. They had only recently been built, and contained the latest service devices.

There was no one in the hall. The doctor pressed the lift-bell impatiently, and when the lift arrived questioned the uniformed attendant sharply.

"Flat 11. Count Foscatini. There's been an accident there, I understand." The man stared at him.

"First I've heard of it. Mr Graves - that's Count Foscatini's man - went out about half an hour ago, and he said nothing."

"Is the Count alone in the flat?"

"No, sir, he's got two gentlemen dining with him."

"What are they like?" I asked eagerly.

We were in the lift now, ascending rapidly to the second floor, on which Flat 11 was situated.

"I didn't see them myself, sir, but I understand that they were foreign gentlemen." He pulled back the iron door, and we stepped out on the landing. No. 11 was opposite to us. The doctor rang the bell. There was no reply, and we could hear no sound from within. The doctor rang again and again; we could hear the bell trilling within, but no sign of life rewarded us.

"This is getting serious," muttered the doctor. He turned to the lift attendant.