'That is possible of course. Yet I have a strong idea that they left by the window.'

'I think you are wrong.'

'Perhaps, mon ami.'

I mused, thinking over the new field of conjecture that Poirot's deductions had opened up to me. I recalled my wonder at his cryptic allusion to the flowerbed and the wristwatch. His remarks had seemed so meaningless at the moment, and now, for the first time I realized how remarkably, from a few slight incidents, he had unravelled much of the mystery that surrounded the case. I paid a belated homage to my friend.

'In the meantime,' I said, considering, 'although we know a great deal more than we did we are no nearer to solving the mystery of who killed Mr. Renauld.'

'No,' said Poirot cheerfully. 'In fact we are a great deal farther off.'

The fact seemed to afford him such peculiar satisfaction that I gazed at him in wonder. He met my eye and smiled.

Suddenly a light burst upon me.

'Poirot! Mrs Renauld! I see it now. She must be shielding somebody.'

From the quietness with which Poirot received my remark, I could se that the idea had already occurred to him.

'Yes,' he said thoughtfully. 'Shielding someone-or screening someone. One of the two.'

Then, as we entered our hotel he enjoined silence on me with a gesture.