‘You are awake very early, mademoiselle?’

‘I haven’t been to sleep really properly. I was just getting that desperate feeling that one does get at five in the morning.’

‘It’s not quite so early as that!’

‘It feels like it! Now then, my super-sleuth, what are we looking at?’

‘But observe, mademoiselle, footprints.’

‘So they are.’

‘Four of them,’ continued Poirot. ‘See, I will point them out to you. Two going towards the window, two coming from it.’

‘Whose are they? The gardener’s?’

‘Mademoiselle, mademoiselle! Those footmarks are made by the small dainty high-heeled shoes of a woman. See, convince yourself. Step, I beg of you, in the earth here beside them.’

Susan hesitated a minute, then placed a foot gingerly on to the mould in the place indicated by Poirot. She was wearing small high-heeled slippers of dark brown leather.

‘You see, yours are nearly the same size. Nearly, but not quite. These others are made by a rather longer foot than yours. Perhaps Miss Chevenix-Gore’s—or Miss Lingard’s—or even Lady Chevenix-Gore’s.’

‘Not Lady Chevenix-Gore—she’s got tiny feet. People did in those days—manage to have small feet, I mean. And Miss Lingard wears queer flat-heeled things.’

‘Then they are the marks of Miss Chevenix-Gore. Ah, yes, I remember she mentioned having been out in the garden yesterday evening.’

He led the way back round the house.

‘Are we still sleuthing?’ asked Susan.

‘But certainly. We will go now to Sir Gervase’s study.’

He led the way. Susan Cardwell followed him.

The door still hung in a melancholy fashion. Inside, the room was as it had been last night. Poirot pulled the curtains and admitted the daylight.

He stood looking out at the border a minute or two, then he said:

‘You have not, I presume, mademoiselle, much acquaintance with burglars?’

Susan Cardwell shook her red head regretfully.

‘I’m afraid not, M. Poirot.’

‘The chief constable, he, too, has not had the advantages of a friendly relationship with them. His connection with the criminal clases has always been strictly official. With me that is not so. I had a very pleasant chat with a burglar once. He told me an interesting thing about french windows—a trick that could sometimes be employed if the fastening was sufficiently loose.’

He turned the handle of the left-hand window as he spoke, the middle shaft came up out of the hole in the ground, and Poirot was able to pull the two doors of the window towards him. Having opened them wide, he closed them again—closed them without turning the handle, so as not to send the shaft down into its socket. He let go of the handle, waited a moment, then struck a quick, jarring blow high up on the centre of the shaft. The jar of the blow sent the shaft down into the socket in the ground—the handle turned of its own accord.

‘You see, mademoiselle?’

‘I think I do.’

Susan had gone rather pale.

‘The window is now closed. It is impossible to enter a room when the window is closed, but it is possible to leave a room, pull the doors to from outside, then hit it as I did, and the bolt goes down into the ground, turning the handle. The window then is firmly closed, and anyone looking at it would say it had been closed from the inside.’