There Is Someone Behind the Door(1960)

For medical advice, Carlos and his wife, Julia go on vacation to a fashion beach. The hotel gets a new host, Roldós, known seducer of scandalous history that lives in the suite next to the couple. Julia hears a piano melody and below the door finds a message asking her to meet in one place. Faced with this audacity, Julia reacts with dignity but curiousity as well. The recklessness of the seducer gets to the point that Carlos realizes this 'relationship' causing a scene of jealousy. Blinded by deception, the follows the supposed rival and Julia and the other people in the hotel heard gunshots. An inspector arrives to investigate the disappearance of Roldós and all suspicion falls on Carlos.