Count Almaviva, posing as a student, “Lindoro,” serenades the beautiful Rosina from outside her window. Rosina is the ward of Dr. Bartolo, who intends to marry her and get her dowry. Rosina, under Dr. Bartolo’s watchful eye, does not appear at the window. Disappointed at her non-appearance, the Count engages the help of Figaro, Seville’s barber and general factotum. Figaro, faced with the prospect of a monetary reward and besting Dr. Bartolo, is quick to offer his assistance. The barber devises a clever plan: The Count will disguise himself as a drunken soldier billeted at the doctor’s house, thereby gaining access to the object of his desire. Meanwhile, Rosina, touched by the serenading voice, resolves to outwit Dr. Bartolo.
In a military uniform and behaving the drunk, Almaviva thwarts all of the Bartolo’s attempts to dismiss him, while simultaneously revealing to Rosina his “true” identity as Lindoro. The doctor summons the police to get rid of the soldier. Discreetly conveying his true status to the officers, the Count is not arrested, to the astonishment of the others.
Count Almaviva returns to Dr. Bartolo’s residence, this time posing as a music teacher, “Don Alonso.” He claims to be substituting for Don Basilo, who is ill, and insists on giving Rosina a music lesson. Figaro distracts Bartolo by shaving him. When Don Basilo enters, obviously not sick, the group convinces the professor that he actually does have scarlet fever. Finally alone in their lesson, the Count and Rosina make plans to elope. Dr. Bartolo shoos Figaro and Almaviva out, as he, himself, makes plans to marry Rosina that very evening. Bartolo convinces Rosina that Lindoro is Count Almaviva’s flunky.
Almaviva and Figaro return again, now disguised in cloaks. They must convince Rosina that the Count’s intentions are honorable, even though she knows him only as “Lindoro.” Dr. Bartolo, however, has removed their ladder as he left to make his own wedding arrangements.
When Don Basilio arrives with a notary—sent to officiate Dr. Bartolo’s marriage to Rosina—Count Almaviva bribes them into officiating his ceremony instead. Rosina and Almaviva have just finished their vows when Dr. Bartolo rushes in with the police. The plot is explained and, learning that the Count will allow him to keep Rosina’s dowry, Dr. Bartolo is appeased.