where did they hide the horse and why? who was John byro? Why did he come to the narrator's house?

They hid the horse in old barn of a deserted vineyard, where they found some food for the horse like oats.

John Bryo was an Assryian farmer whose horse was stolen by Aram and Mourad. He was a good friend of their family and he made the children realise that the act of stealing was bad deed.

He came to the narrator's house to inform that he got the horse back and it had become more stronger and better to ride.

Hope this helps you!