Beautiful but Dangerous (also released as La donna più bella del mondo/ The World's Most Beautiful Woman) is a 1956 French-Italian film directed by Robert Z. Leonard. The picture is a biopic about Italian opera soprano Lina Cavalieri. The film was a co-production between Italy (where it was released as La donna più bella del mondo) and France (where is known with the title La belle des belles). For this film, Gina Lollobrigida was awarded with a David di Donatello for Best Actress.
Lina (Gina Lollobrigida) is an orphan, brought up by her adopted mother who trains her for music. Her mother becomes sick due to a heart attack on the stage, and Lina goes to the stage in place of her mother. A group teases her and will not allow her to perform. From the balcony, the prince of Russia, Sergio (Vittorio Gassman) comes down and makes the group leave the theater and asks Lina to perform. It is a vgood performance, but at the end, she finds out that her mother had another attack, and has been sent to the long distance hospital. By the night she wants to go, but there is no way to make it. Sergio offers her lift to the hospital, and on the way, they get to know each other. The prince does not tell Lina his identity but will say only that he came there for horse competition in the local club, and he stays regularly in Paris and he is from Russia. After reaching the hospital, she leaves her handbag in the coach. Sergio puts money and his golden ring in the bag and gives it to Lina. She hurries into the hospital and discovers her mother has died.
Next, she enters the horse riding club and finds out Sergio stood first in the competition. She also discovers that he is the prince. She returns the money and the ring back to him, but he says that he will take all the things in Paris.
She goes back to her music school in Rome and asks for the best teacher, and she is ready to pay anything. They recommend Doria (Robert Alda) who trains her and brings her to Paris. Doria is in love with Lina, but Lina is in love with Sergio. She refuses Doria and leaves him. She struggles to get a chance and finally settles down to some extent with Carmela (Anne Vernon). One of the singers is jealous of her and then is fired from the opera for her. They fight, and after seeing this fight, one of the members gets the idea to make a live show of shored fighting in between the two ladies to earn money. Lina owns the competition, and there a famous music director Silvani (Mario Del Monaco) meets her and invites her to the theater. From the stage, Lina’s name becomes famous as ‘the knight’.
One day Doria comes and expresses his love for her again, but she refuses. Before a stage show, she notices in the balcony the prince is there. She is thrilled. At the end of the show, she expects a bouquet of flowers from the prince, but nothing is there. She is disappointed. Silvani comes and invites both the friends for a party at his house. As they agree to go, the representative of the Prince comes and sends the message that the prince has arranged a party in the honour of Lina. She accepts the offer and meets the prince.
In an intimate situation, the prince is trying to say something to Lina, but she is not in the mood to listen. Suddenly the friends of the prince knock on the door, and overhearing the words from them, Lina misunderstands the prince and thinks that he is going to marry someone else in Russia. She leaves him and leaves Paris for an unknown place.
In a village side nearby Paris, Lina, Carmela stay together and Silvani comes to teach her extensive lesions on opera music. Before leaving for Paris, Silvani says that he loves Lina, and she need not to answer him right then. If at all, any time in life she feels for him, he is there for her. Silvani meets an opera whose music director was Doria, where they will arrange for Lina to sing. Doria becomes jealous of Silvani.
In between the show, Sergio meets Lina in the dressing room. He refused his uncle’s marriage proposal for him and came to spend life with Lina. Lina refuses him because of her misconception of the prince, and in front of Silvani, she says that she will marry him after the show. Doria appoints someone to kill Silvani during the scene of a firing squad.
Silvani dies, Lina thinks Sergio killed him, and Doria understands that she doesn't suspect him. So now for him, he will take her to a stage show in a different part of the world, and then an invitation comes from the tsar of Russia.
On the way to Russia, due to snowfall, the train halts for two hours, and there Sergio meets her again. However, this time she accuses him of the murder of Silvani. Extremely insulted, Sergio leaves.
During the meeting with the tsar and his wife, Lina sees Sergio, and she says that she wants to sing a new opera, the last performance with Silvani. Doria objects, but the Quinn shows her interest for that.
During the performance, Doria is tense because he arranged the murder of Silvani. Lina is doing extremely well because she is emotionally charged, and Prince Sergio feels disgusted because he thinks that Lina is creating pressure on him unnecessarily. He admits to Lina that it was he plotted the murder of Silvani out of jealousy.
Finally, Lina goes back to the prince and both of them walk away.