The prepositional phrase is "over the hill". In this case it consists of a preposition (over) and a noun phrase (the hill). It relates to the word "come". It is worth mentioning that you´ll never find a subject in a prepositional phrase, you find the object it refers to.
Other examples:
-We will return in a few months.
-Tom is the boy in a green shirt.
-I saw a very nice painting by Picasso.
-I gave some candies to the kids on the corner.