 Initially, Polanski wanted to make a criminal story about a couple  which takes a young hitchhiker to a boat trip, and at the end the  boy dies in mysterious circumstances. In his version the trip was  about a week long a involved some other characters. It was  Jerzy Skolimowski (qv) who proposed to shorten it to one day and  limit the number of characters. The final script was created in only  three, four days by Polanski, Skolimowski and Jakub Goldberg (qv)  in Polanskis apartment. While writing the script they were playing  the dialogue, changing the roles all the time.