The Marriage of Figaro by Wolfgang Amadeus Mozart

Three years prior, Figaro helped Count Almaviva marry Rosina, whom he abducted from her unscrupulous guardian, Dr Bartolo.

Figaro and Susanna, servants to Count Almaviva, are soon to be married. Susanna fears the Count will try to bed her before their wedding night but Figaro vows to thwart his schemes. In a further complication, Marcellina, Dr Bartolo’s old house keeper, is insisting Figaro marry her as payment for an overdue loan. The Count’s page, Cherubino is in trouble for dallying with the gardener’s daughter and seeks Susanna’s help. He hides when the Count arrives to woo Susanna, but is discovered. The Count resolves to send him away to the military.
The Countess laments her husband’s infidelity, but Figaro has a plan. He has told the Count in an anonymous letter that the Countess is meeting a lover that evening. In fact, it will be Cherubino, disguised as a girl. The Count, lured to the garden by Susanna, will be found out and humiliated. However, he suddenly appears as they are dressing Cherubino, who escapes through the window. The Countess reveals the plan to her husband but Figaro denies it. Marcellina arrives to demand that Figaro marry her and the Count orders him to honour his promise.
Susanna and the Countess devise their own plan to entrap the Count. They send him a letter, inviting him to meet Susanna that night in the garden, but in reality they will swap places.
Figaro argues he cannot marry Marcellina without his parents’ permission – impossible to obtain as he was stolen from them as a baby. Marcellina realises Figaro is her long-lost son: she will marry the father, Bartolo, and Figaro and Susanna’s wedding can proceed. Barbarina, the gardener’s daughter, gets the Count’s permission to marry Cherubino, and all three couples are married.
Unaware of the new plan, Figaro believes Susanna is betraying him on their wedding night when he finds out she is meeting the Count in the garden that evening. “Susanna” (the Countess in disguise) arrives for her rendezvous with the Count, who is delighted to see her. Figaro is furious.
The “Countess” (Susanna in disguise) appears. Figaro eventually recognises his bride and they play out a fake seduction to trick the Count, who shouts for the guards to arrest Figaro. The actual Countess then reveals herself and the Count, caught red-handed in trying to seduce “Susanna”, begs his wife to forgive him.