Escaping from a distasteful marriage, Nanki-Poo, the son of the Mikado, arrives in the town of Titipu - disguised as a musician. He has chosen Titipu because a beautiful girl, Yum-Yum, with whom he has fallen in love, lives in the town. A desire to marry Yum-Yum, however, is not enough. Nanki-Poo has to contend with her guardian, Ko-Ko, the Lord High Executioner, who has every intention of marrying Yum-Yum, himself. Problems are compounded when the Mikado, accompanied by Katisha, Nanki-Poo's jilted bride, also arrive in the hitherto peaceful town of Titipu.