That way, she can tell him about them, because he's on a quest to reach his wife.
Was thinking about making it "The Thief and His Master" and so a father looking for his son, but then, no -- the father set out from the kingdom he's going to. So, the wife.
Except, on reflection, I don't know of a Quest for the Lost Husband that involves those three. The Sun, the Moon, and the Wind or Stars, yes -- or three old witches -- or the North, South, East, and West Winds, but not those three.
Looks like I shall contaminate the tale, as folklorists put it.