describe santiagos first interaction with the alchemist?

Walking home from his meeting with the chiefs Santiago is pensive but sure that he has made the right decision. Suddenly, he is assailed by a man with a falcon on his shoulder, dressed all in black, riding a white horse. The man holds a sword to Santiago's head and demands to know how he knew of the coming of the army. Santiago, frightened, explains to the man about the omens of the desert and his Personal Legend, concluding that he had no choice. The man understands completely, to Santiago's surprise, and takes his leave, telling Santiago to come see him if he survives the coming days. As the horseman rides away, Santiago realizes that he has just met the alchemist.