Cuando acaba la noche.

In a New York hospital, a man is cured of heroin addiction after a grueling three-month treatment. Although no longer an addict, he has complete amnesia: the only clues to his past are an expensive ring he was wearing when admitted, and a book of matches from a Puerto Rican nightclub. He pawns the ring and buys clandestine passage on a boat to Puerto Rico in search of his identity.