First, who killed Morris Barnes?
Secondly, when was it done?
Thirdly, where was it done?
I have left out a possible fourth, why was it done?
because, in this case, I think that the motive and the man are practically identical.

I mean that if you discover one, you discover the other." Heneage leaned across the table towards the Colonel.
"You are a magician, Colonel," he declared quietly.

"I glanced through this case in the paper, and it did not even interest me.

Since I have listened to you I have fallen under the spell of the mysterious.

Have you any theories ?" The Colonel's face fell a little.
"Well, I am afraid not," he admitted regretfully.