Alfonso and Luisa, a young couple whose marriage is undergoing considerable strain, during a car journey in the south, come across a strange traveler, a mysterious satanical being who travels the world over with a ruck-sack full of strange objects, including a magical music box. This kind of demon-god upsets the couples’ plans and projects and even reveals their heart’s innermost and most obscure secrets, arousing in them and through them sparks of pity, true feeling and physical involvement. The strange foreigner, however, receives in exchange death: he is killed by Alfonso and Lisa. But his magical powers are all condensed in the music box that remains in the car and this causes the car, which the couple uses in a vain attempt to return home, to explode.