"As you're aware, I'm a bit of a mountaineer--you know that I've spent a good many of my holidays in Switzerland, climbing.
Consequently, I know what alpenstocks and ice-axes are.

And when I came to reflect on the circumstances of Crone's murder, I remember that not so long since, happening to be out along the riverside, I chanced across Sir Gilbert Carstairs using a very late type of ice-ax as a walking-stick--as he well could do, and might have picked up in his hall as some men'll pick up a golf-stick to go walking with, and I've done that myself, hundred of times.

And I knew that I had an ice-ax of that very pattern at home--and so I just shoved it under the doctor's nose in court, and asked him if that hole in Crone's head couldn't have been made by the spike of it.

Why?
Because I knew that Carstairs would be present in court, and I wanted to see if he would catch what I was after!" "And--you think he did ?" asked the superintendent, eagerly.
"I kept the corner of an eye on him," answered Mr.Lindsey, knowingly.
"He saw what I was after! He's a clever fellow, that--but he took the mask off his face for the thousandth part of a second.

I saw!" The two listeners were so amazed by this that they sat in silence for a while, staring at Mr.Lindsey with open-mouthed amazement.
"It's a dark, dark business!" sighed Murray at last.