Il prigioniero ("The Prisoner") is an opera (originally a radio opera) in a prologue and one act, with music and libretto by Luigi Dallapiccola.
 The opera was first broadcast by the Italian radio station RAI on 1 December 1949.
 The work is based on the short story "La torture par l'espérance" ("Torture by Hope") from the collection "Nouveaux contes cruels" by the French writer Auguste Villiers de l'Isle-Adam and from "La Légende d'Ulenspiegel et de Lamme Goedzak" by Charles de Coster.
 Some of the musical material is based on Dallapiccola's earlier choral work on a similar theme, "Canti di prigionia" (1938).
 Dallapiccola composed "Il prigioniero" in the period of 1944–1948.
 The work contains seven parts and lasts about 50 minutes.
 The musical idiom is serialism, and it is one of the first completed operas using that compositional method.
La Dame aux Camélias (literally The Lady with the Camellias, commonly known in English as Camille) is a novel by Alexandre Dumas, "fils", first published in 1848, and subsequently adapted by Dumas for the stage.
 "La Dame aux Camélias" premiered at the Théâtre du Vaudeville in Paris, France on February 2, 1852.
 The play was an instant success, and Giuseppe Verdi immediately set about putting the story to music.
 His work became the 1853 opera "La Traviata", with the female protagonist, Marguerite Gautier, renamed Violetta Valéry.
Henry Landau OBE was a South African World War I volunteer who served with the British Army's Royal Field Artillery when he was recruited into what is now known as the SIS (MI6).
 He was notable for handling one of the most effective espionage networks of the First World War, La Dame Blanche, and later wrote a number of bestselling novels about his experiences during the war.
The Emprise de l'Escu vert à la Dame Blanche ("Enterprise of the Green Shield with the White Lady") was a chivalric order founded by Jean Le Maingre and twelve other knights in 1399, committing themselves for the duration of five years.
 Inspired by the ideal of courtly love, the stated purpose of the order was to guard and defend the honor, estate, goods, reputation, fame and praise of all ladies, including widows.
 It was an undertaking that earned the praise of Christine de Pizan.
La dame blanche ("The White Lady") is an opéra comique in three acts by the French composer François-Adrien Boieldieu.
 The libretto was written by Eugène Scribe and is based on episodes from no fewer than five works of the Scottish writer Sir Walter Scott, including his novels "The Monastery", "Guy Mannering", and "The Abbot".
 The opera has typical elements of the Romantic in its Gothic mode, including an exotic Scottish locale, a lost heir, a mysterious castle, a hidden fortune, and a ghost, in this case benevolent.
 The work was one of the first attempts to introduce the fantastic into opera and is a model for works such as Giacomo Meyerbeer's "Robert le diable" and Charles Gounod's "Faust".
 The opera's musical style also heavily influenced later operas like "Lucia di Lammermoor", "I puritani" and "La jolie fille de Perth".
Ulisse is an opera in a prologue and two acts composed by Luigi Dallapiccola to his own libretto based on the legend of Ulysses.
 It premiered at the Deutsche Oper in Berlin (in German translation by Karl-Heinrich Kreith as "Odysseus") on 29 September 1968 conducted by Lorin Maazel with Erik Saedén in the title role.
 "Ulisse" was Dallapiccola's last opera and took eight years to compose.
 As in his previous operas, "Volo di notte" and "Il prigioniero", his declared theme was "the struggle of man against some force much stronger than he".
The Forest of Chailluz is a wooded area comprising 1,673 hectares, located in Besançon, in the Doubs, France.
 It is bisected by Highway A36.
 Its elevation ranges from 319 m around Thise to 619 m at the Fort de la Dame Blanche.
La Dame Blanche (French; literally "The White Lady") was the codename for an underground intelligence network which operated in German-occupied Belgium during World War I.
 It took its name from a German legend which stated that the fall of the Hohenzollern dynasty would be announced by the appearance of a woman wearing white.
The Opéra-Comique is a Parisian opera company, which was founded around 1714 by some of the popular theatres of the Parisian fairs.
 In 1762 the company was merged with, and for a time took the name of its chief rival the Comédie-Italienne at the Hôtel de Bourgogne, and was also called the Théâtre-Italien up to about 1793, when it again became most commonly known as the Opéra-Comique.
 Today the company's official name is Théâtre national de l'Opéra-Comique, and its theatre, with a capacity of around 1,248 seats, sometimes referred to as the Salle Favart (the third on this site), is located in Place Boïeldieu, in the 2nd arrondissement of Paris, not far from the Palais Garnier, one of the theatres of the Paris Opéra.
 The musicians and others associated with the Opéra-Comique have made important contributions to operatic history and tradition in France, and to French opera.
 Its current mission is to reconnect with its history, and discover its unique repertoire, to ensure production and dissemination of operas for the wider public.
 Mainstays of the repertory at the Opéra-Comique during its history have included the following works which have each been performed more than 1,000 times by the company: "Cavalleria Rusticana", "Le chalet", "La dame blanche", "Le domino noir", "La fille du régiment", "Lakmé", "Manon", "Mignon", "Les noces de Jeannette", "Le pré aux clercs", "Tosca", "La bohème", "Werther" and "Carmen", the last having been performed more than 2,500 times.
Cinque variazioni ("Five variations") is a composition for solo piano by Luciano Berio, written in 1952/3 and greatly revised in 1966.
 It was published by Suvini Zerboni and the first performance was given by Berio in Milan in 1953.
 The variations are based on a three-note melodic cell—""fratello""[014]—from the opera "Il prigioniero" by Luigi Dallapiccola, to whom the work is dedicated .
 Major changes between the two versions are indicated below, but many other small changes may be found, mostly additions to render the harmony more complex.

Question: What do La dame blanche and Il prigioniero have in common?
Answer: opera