Lucia is a mature woman who maintains a relationship with the young John. When he is found murdered in a bullring with a nail stuck in his chest, Lucia is the prime suspect, it is believed that the motive for the crime was jealousy because it felt for her daughter Marta, which had also been seduced by John.

John is a shy and good-natured man who lives in Ceuta and does everything by correspondence, from studying a career or learning judo to getting a girlfriend. She is from Madrid and the time has come for Juan to meet her so he takes a boat to the peninsula. In the boat he coincides with Maria, a beautiful young woman who goes to the capital to study chant and which he had previously met accidentally. During the trip, foreign smugglers try to use John to pass inadvertently stolen diamonds in Tangier.