The story is set in the home of Lisídamo, an old and greedy man who has fallen in love with the young orphan Casina. Casina was brought up as a housemaid, but Lisídamo is not the only one who wants to marry her. His son Eftinico is also in love with her.
To avoid arousing suspicion, Lisídamo plans to marry Casina off to his steward, Olímpico. The arrangement is self-serving: on the first wedding day, Olímpico is to cede his marital rights to Lisídamo. Lisídamo's wife, Cleóstrata, discovers the plan and proposes an alternative: to marry Casina to Cálino, her son's servant.
As the dispute within the household cannot be resolved, the matter is ultimately decided by drawing lots. This leads to a farce involving disguises, darkness, false identities and a revenge plot by the women of the house, intended to turn Lisídamo's plans on their head. The performance is presented by the Noite Bohemia theatre company and forms part of a programme for the exchange of amateur theatre.