Eisenstein is due to report to prison for a misdemeanour but is induced by his friend Dr Falke to attend a fancy dress party at Prince Orlofsky's. Falke plans revenge on Eisenstein for having abandoned him on a previous occasion to go home drunk in the costume of a bat. Eisenstein's wife Rosalinde thinks the coast is clear for a rendezvous with her young lover Alfred, who is mistaken by Frank, the prison governor, for her husband and taken to prison. Adele the chambermaid has sought various excuses for taking time off and in a borrowed dress attends Prince Orlofsky's party, where Rosalinde also appears, disguised as a Hungarian countess. In a play of disguises and partly mistaken identities, the cast moves from Prince Orlofsky’s party to the prison where Eisenstein will confront his wife and, realising he has been duped by Falke, philosophically decides to blame it all on the champagne…