A crowd has gathered at the walls of Peking awaiting the execution of Turandot's latest victim, the Prince of Persia.  Another young prince, Calaf, who is unknown to the people of Peking, enters the scene.  In the midst of the crowd he recognizes his father Timur, an exiled Tartar King, who has fallen down from exhaustion.  The King is accompanied by a young slave girl, Liu, who is secretly in love with Calaf.  Only Timur and Liu know the true identity of Calaf.  The crowd cries out for Turandot to spare the Prince of Persia, but Turandot appears and signals for the execution to be carried out.  As soon as Calaf sees Turandot, he falls deeply in love with her and all the elements of a 'heroic quest' begin.  The three ministers, Ping, Pang and Pong, try to discourage Calaf from accepting the challenge to solve the riddles, but they fail.  (The three ministers are comical characters derived from the tradition of commedia dell'arte and provide a direct contrast with the very serious and noble characters of Turandot and Calaf.)  Timur and a tearful Liu also beg Calaf not to risk his life, but as Act I closes, Calaf bravely strikes the gong which announces that he is the new suitor.  

Act II

Scene I: A palace pavilion
At the royal palace, the three ministers prepare both a wedding ceremony and a funeral ceremony in anticipation of Calaf's fate.  In a fit of depression the three men reminisce about how happy they were before the birth of Turandot when China was not plagued by her horrible executions.  They pray that love will conquer her heart and peace will return once again.  

Scene II: In the palace
In the palace courtyard, the Old Emperor Altoum, Turandot's father, sits high on a throne.  He vainly asks Calaf to reconsider.  Turandot enters, and with the aria 'In questa reggia' (In this kingdom) she explains that she wishes to avenge the rape and murder of her ancestor Lou-ling who was abducted by a conquering Prince.  It is this incident that has turned Turandot against men forever.  She desires above all else to remain a virgin.  She poses the three riddles to Prince Calaf, and to her absolute horror he solves each of them correctly!  She collapses in despair and pleads with her unyielding father to release her from her own decree.  Still hoping to win her love, Calaf tells Turandot that if she can discover his name by daybreak, he will pay the forfeit and surrender his own life.  

Act III: The palace garden

In the palace garden, Calaf hears Princess Turandot's latest decree: "On pain of death, no one in Peking shall sleep until the name of the unknown Prince is revealed."  Calaf sings the aria 'Nessun dorma'(No one sleeps) reflecting on his firm devotion and love for Turandot and his strong belief that he will conquer her with love.  The mob threatens him with drawn daggers to learn his name.  Ping, Pang, and Pong try to tempt Calaf from his quest with worldly pleasures but fail again.  Suddenly the guards drag in Timur and Liu who had been noticed in the company of Calaf.  Calaf tries to convince the mob that neither of them knows his secret.  Turandot herself tries to question Timur but Liu steps forward saying that she alone knows the true identity of the stranger.  The guards torture Liu but she still does not divulge his name.  Finally Liu tells the Princess Turandot that because of the sacrifice she will now make, Turandot will at last learn to love.  Liu snatches a dagger, stabs herself and dies at the feet of Timur.  Turandot is deeply moved by the selflessness of Liu's expression of love.  Her once cold, cold heart begins to thaw.  Calaf and Turandot are left alone.  They sing a duet that climaxes in a passionate kiss.  The kiss shames the virgin Turandot who weeps, showing emotion for the first time.  She pleads with Calaf to leave her alone forever but he tells her his name, placing his destiny in her hands.  Trumpets announce the coming of dawn and the crowd enters.  Turandot announces joyfully that she knows the name of the unknown stranger, "His name is love!"  The court salutes the power of love and life that has transformed Turandot and restored peace to Peking.