Act I - King Hildebrand's Encampment

King Hildebrand's court is buzzing with excitement as everyone waits the arrival of King Gama and his daughter Ida. She was married to Hilderbrand's son, Hilarion, in their infancy, and today Gama is bound by treaty to bring her to join her husband. There is a rumour, however, that she has forsworn the company of men and has founded a women's university. Hildebrand therefore tells his people to welcome Gama warmly if Ida is with him, but to imprison him if she has broken her troth

Preceded by his three warlike sons, Arac, Guron and Scynthius, King Gama duly arrives - a most disagreeable character (although he says he can't think why!). He sneeringly confirms that Ida has no intention of leaving her university. Hilarion responds by seizing Gama and his sons as hostages. Hilarion announces that aided by his two bosom pals, Cyril and Florian, he will go to Ida's college to try to win her heart. Gama and Co. are loaded with chains and their complaints meet with a spirited ensemble which brings down the curtain.

Act II - The grounds of Ida's University

Lady Psyche, Professor of Humanities, leads a study session involving a bitter attack on "Man, Nature's sole mistake." Lady Blanche, jealous of Ida and believing that she should be the rightful principal, hands out stiff punishment to those students who have broken the rules. Princess Ida enters, movingly invokes the aid of the Goddess Minerva, and extolls her feminist credo. All then leave just before Hilarion and his friends manage to climb in over the outer walls. After picking out the prickles and nettles into which they have fallen, they dress up in some female garments they find, and flounce riotously about. Ida walks in on them and they have no choice but to pretend they are noblewomen wishing to enroll. After extracting their vows never to marry any man, Ida returns to her duties.

Lady Psyche enters - horrors, she is Florian's sister and he has to let her into the secret which she reluctantly agrees to keep. But she still professes in song that "Man at best is only a monkey shaved!" Melissa eavesdrops on the conversation, but also agrees to keep silent since she finds the men much more attractive than she had been led to believe.

Melissa's mother, the formidable and ambitious Lady Blanche, has also seen through the disguise and is furious with her daughter. Melissa persuades her to join in the conspiracy by pointing out that if Ida gets married, she, Blanche, will attain her ambition and take over as principal.

Lunch is now served, but Cyril unfortunately overindulges and gives the game away in a tipsy "kissing song." In her confusion, Ida falls from the wall into the wadi but is rescued by Hilarion. She is nonetheless appalled and orders the imposters' arrest. Rescue is at hand for Hildebrand and his soldiers arrive and destruction and rush in with the captive Arac, Guron and Scynthius. Hildebrand threatens destruction and death if Ida refuses to yield and her brothers beg her not to let them be hanged, but she remains adamant. She is granted a day to think it over and a big defiant ensemble brings the act to a close.

Act III - The Following Day, The College Defences

Although all the girls are now standing to arms and singing "Death to the invader," they are not really happy about the situation, nor confident of the outcome. Despite her efforts at morale boosting, Ida bitterly realizes she cannot rely on her feminine troops.

Hildebrand, loth to make war on women, proposes a combat between Gama's sons and Hilarion and his friends to decide the issue. Ida has little choice but to agree. Gama himself bitterly complains of his treatment as a prisoner - the worst of tortures - he's been given nothing whatever to grumble at! Nevertheless he is initially confident of his sons' military abilities, until they rather strangely prepare for the fight by removing all their hot and bothersome armour. The battle is short and decisive - Hilarion, Cyril and Florian are easy victors. Ida, despite her lingering doubts, admits the possibility of coexistence with men and resigns herself to Hilarion. Music fills the air as the curtain falls.