It appeared to excite the liveliest contempt in Dr Tosswill, who drew me aside, literally snorting with rage.

‘Balderdash, sir,’ he exclaimed angrily. ‘Pure balderdash. The man’s an imposter. He doesn’t know the difference between the superstitions of the Middle Ages and the beliefs of Ancient Egypt. Never have I heard such a hotch-potch of ignorance and credulity.’

I calmed the excited expert, and joined Poirot in the tent. My little friend was beaming cheerfully.

‘We can now sleep in peace,’ he declared happily. ‘And I can do with some sleep. My head, it aches abominably. Ah, for a good tisane!’

As though in answer to prayer, the flap of the tent was lifted and Hassan appeared, bearing a steaming cup which he offered to Poirot. It proved to be camomile tea, a beverage of which he is inordinately fond. Having thanked Hassan and refused his offer of another cup for myself, we were left alone once more. I stood at the door of the tent some time after undressing, looking out over the desert.

‘A wonderful place,’ I said aloud, ‘and a wonderful work. I can feel the fascination. This desert life, this probing into the heart of a vanished civilization. Surely, Poirot, you, too, must feel the charm?’

I got no answer, and I turned, a little annoyed. My annoyance was quickly changed to concern. Poirot was lying back across the rude couch, his face horribly convulsed. Beside him was the empty cup. I rushed to his side, then dashed out and across the camp to Dr Ames’s tent.

‘Dr Ames!’ I cried. ‘Come at once.’

‘What’s the matter?’ said the doctor, appearing in pyjamas.

‘My friend. He’s ill. Dying. The camomile tea. Don’t let Hassan leave the camp.’

Like a flash the doctor ran to our tent. Poirot was lying as I left him.

‘Extraordinary,’ cried Ames. ‘Looks like a seizure—or—what did you say about something he drank?’ He picked up the empty cup.

‘Only I did not drink it!’ said a placid voice.

We turned in amazement. Poirot was sitting up on the bed. He was smiling.

‘No,’ he said gently. ‘I did not drink it. While my good friend Hastings was apostrophizing the night, I took the opportunity of pouring it, not down my throat, but into a little bottle. That little bottle will go to the analytical chemist. No’—as the doctor made a sudden movement—’as a sensible man, you will understand that violence will be of no avail. During Hastings’ absence to fetch you, I have had time to put the bottle in safe keeping. Ah, quick, Hastings, hold him!’

I misunderstood Poirot’s anxiety. Eager to save my friend, I flung myself in front of him. But the doctor’s swift movement had another meaning. His hand went to his mouth, a smell of bitter almonds filled the air, and he swayed forward and fell.

‘Another victim,’ said Poirot gravely, ‘but the last. Perhaps it is the best way. He has three deaths on his head.’