As we sat down at the dinner table and plates of white gluey liquid were set before us, I let my eyes rove round the table while I summed up the possibilities. If Poirot were right and retained his clearness of brain unimpaired, one of these people was a dangerous murderer - and probably a lunatic as well. Poirot had not actually said so, but I presumed that X was probably a man. Which of these men was it likely to be?

Surely not old Colonel Luttrell, with his indecision and his general air of feebleness. Norton, the man whom I had met rushing out of the house with field glasses? It seemed unlikely. He appeared to be a pleasant fellow, rather ineffective and lacking in vitality. Of course, I told myself, many murderers have been small insignificant men - driven to assert themselves by crime for that very reason. They resented being passed over and ignored. Norton might be a murderer of this type. But there was his fondness for birds. I have always believed that a love of nature was essentially a healthy sign in a man.

Boyd Carrington? Out of the question. A man with a name known all over the world. A fine sportsman, an administrator, a man universally liked and looked up to. Franklin I also dismissed. I knew how Judith respected and admired him. Major Allerton now. I dwelt on him appraisingly. A nasty fellow if I ever saw one!

The sort of fellow who

would skin his grandmother. And all glossed over with this superficial charm of manner. He was talking now - telling a story of his own discomfiture and making everybody laugh with his rueful appreciation of a joke at his expense. If Allerton was X, I decided, his crimes had been committed for profit in some way.

It was true that Poirot had not definitely said that X was a man. I considered Miss Cole as a possibility. Her movements were restless and jerky - obviously a woman of nerves. Handsome in a hag-ridden kind of way. Still, she looked normal enough. She, Mrs. Luttrell and Judith were the only women at the dinner table. Mrs. Franklin was having dinner upstairs in her room, and the nurse who attended to her had her meals after us.

After dinner I was standing by the drawing-room window looking out into the garden and thinking back to the time when I had seen Cynthia Murdoch, a young girl with auburn hair, run across that lawn. How charming she had looked in her white overall...

Lost in thoughts of the past, I started when Judith passed her arm through mine and impelled me with her out of the window onto the terrace. She said abruptly, "What's the matter?"

I was startled. "The matter? What do you mean?"

"You've been so queer all through the evening. Why were you staring at everyone at dinner?"

I was annoyed. I had had no idea I had allowed my thoughts so much sway over me.