Figaro sends an anonymous letter to the Count, warning him of adulterers, in the hopes of distracting him during the wedding that evening.
The Countess is lamenting her husband’s infidelity when Susanna arrives with Cherubino, planning to disguise him as a woman and entrap the Count in an act of infidelity. As they are finding a dress for him, the Count suddenly appears, highly suspicious after reading Figaro’s letter. Cherubino only just escapes.
Marcellina arrives to demand that Figaro honours his promise and marry her. The Count happily announces that the wedding is postponed until Figaro’s debt is resolved.