What fewer commentators noticed was the brilliance of the musical architecture. Sorozábal's transformations of original Russian folk material gives his work a symphonic tautness and economy. The ubiquitous Song of the Volga Boatmen turns up in various guises; for example, in the rocking accompaniment to the Prince's lovely Romanza: "Es delicada flor"; and as the melody of Katiuska's radiant nocturne "Noche Hermosa". By these means, the composer produced a work that is musically even more impressive than the sum of its parts.
Act 1 - An Inn in the Ukraine, soon after the Bolshevik revolution. Groups of dispossessed farmworkers troop in from the countryside (Coro: "Todo es camino".) The royalist innkeeper Boni promises to aid them, and listens to their harrowing stories about the Red Army, a detachment of which has burned the castle of Prince Sergio, former ruler of the region. Pedro Stakof, the Soviet Commissar newly arrived from Kiev, arrives at the snug little inn without identifying himself. Despite his revolutionary fervour, he yearns for the peace of a quiet home and the love of a good woman (Romanza: "Calor de nido".) He announces that the Prince, his courtiers and other condemned nobles have escaped and have taken refuge in the area. Boni and his fiancée Olga recall happier times with ex-colonel Bruno Brunovich of the Kazan cossacks (Terceto: "El cosaco en su brioso corcel".) The Catalan stocking salesman to the Czar, Amadeo Pich, seeks refuge at the Inn; as does Prince Sergio accompanied by a young girl, Katiuska. Everyone greets him joyfully and Bruno offers him refuge, but since he has a price on his head he selflessly asks only that Katiuska be cared for (Coro y Romanza: "Es el príncipe ... es delicada flor"). Katiuska recounts her sad story in a touching song (Romanza: "Vivía sola".) The red hordes devastated her house and killed her grandmother leaving no choice but flight. As he leaves the Prince gives Bruno funds to take care of Katiuska, but in reality the corrupt ex-colonel is more interested in simply pocketing the money.
Just as everyone is settling down for the night (Concertante: "Ya anocheció, ya no debéis partir",) a troop of Red Army soldiers arrive looking for drink. Katiuska, believing the Prince has been captured, comes out of hiding and the soldiers pounce on her. At that moment Pedro arrives. He defends the girl, threatening the soldiers, and eventually persuades them to leave by appealing to their patriotism in the vigorous Canción: "La mujer rusa". Katiuska begs Pedro to let her take care of a fleshwound he has received in the shoulder, but Pedro leaves to make sure that everything is quiet. The farmers want to take the opportunity to get away, but eventually listen to Katiuska and settle down again for the night. Bruno plots to abscond with Olga and the money, whilst Pich offers to join in the plan. Soon afterwards Pedro reappears to thank Katiuska for helping him, but vanishes again when he hears shooting. Katiuska prays for his safety, but when she hears another burst of firing she is left in despair as the act ends in general confusion (Final: "El reloj las diez ya dio".)
Act 2.In an attempt to calm the situation Iván, an itinerant old accordionist, accompanies Olga and the farmers in a nostalgic, yearning song about their homeland (Cancion y coro: "Ucraniano de mi amor".) Iván appears to know Katiuska and tells Olga that he will return to reveal his reasons the following day. Katiuska, who cannot sleep, sings a song in praise of the beautiful Ukrainian night (Romanza: "Noche hermosa".) whilst the lecherous Bruno and Pich lead a jazzy Boston Waltz in praise of Russian women, ironically countered by Olga (Cuarteto: "Rusita, rusa divina".) At midnight, however, Pedro reappears with his soldiers, bringing the Prince in a prisoner. They lock him up in one of the bedrooms and set a guard. Katiuska recriminates with Pedro, who stoutly defends his actions and Bolshevik ideals. Left alone together they finally admit their love (Dúo: "Somos dos barcas",) but when Katiuska asks Pedro to save the life of the Prince and leave Russia with them the Commissar sets his face against such treason, and Katiuska breaks down.
A soldier tells Pedro that there is a suspicious concentration of armed men in the forest. Bruno, Olga and Amadeo Pich decide this is the moment to make a move for jazzy Paris (Terceto cómico: "A París me voy".) Before they can get away Pedro and the soldiers return having captured Iván, who is revealed to be a nobleman in disguise, with his insurgent followers.
Katiuska dimly recognises Iván and begins to recall memories of her childhood. Iván reveals to Katiuska her name - Katiuska Ivanova, his daughter. The soldiers want to order the arrest of all the aristocrats, but Pedro prevents them, maintaining that the men are not aristocrats at all, and extending a safe-conduct to all of them. At this crucial moment a Chief Commissar appears on the scene with reinforcements. Pedro is accused of treason and is arrested. However, when he discovers exactly what has happened the Commissar declares that the Prince, Iván and the rest of the nobles are condemned, whilst Katiuska can choose between exile as a Princess and marriage with Pedro Stakoff. As the curtain falls she makes her choice. Pedro and Katiuska rush into one anothers' arms, vowing never to separate ever again (Final: "Esta mujer, tuya nunca ha de ser".)