Holmes makes it all quite clear
During the train journey hack to London, Holmes explained to us how he had solved the mystery.
Any solutions which I reached in London from the newspaper reports were completely wrong.
I thought that Simpson was guilty, although I didn't know all the facts. But when I arrived at Pyland, I realized the importance of the stable boy's meal.
Only a strong tasting meal such as curry can hide the taste of opium. Now, Simpson was a stranger and could not know what the meal was to be.
But clearly Straker knew it was curry, and he had a chance to put the opium in before the cook took it to the stables.
How does this connect with the dog's behaviour?' I asked. The dog's silence proved that it was not a stranger who took the horse away.
Clearly the midnight visitor