Poirot went and sat down in it. “The blue letter you speak of, where was it when you left the room?”

“ Mr. Ackroyd had laid it down on this little table at his right hand.”

Poirot nodded. “Except for that, everything was in its place?”

“Yes, I think so.”

“Colonel Melrose, would you be so extremely obliging as to sit down in this chair a minute. I thank you. Now M. le docteur, will you kindly indicate to me the exact position of the dagger?”

I did so, whilst the little man stood in the doorway.

“The hilt of the dagger was plainly visible from the door then. Both you and Parker could see it at once?”