Konstanze and Blonde are in the power of Selim Bassa, who puts them to work for him. Osmin manages his palace for him and keeps a check on Pedrillo, who also works for the Pasha.
Selim Bassa has fallen in love with Konstanze, Osmin with Blonde.
Pedrillo, who also loves Blonde, wants to help the women, but sees no way of doing so till the appearance of Belmonte, Konstanze's lover.
Pedrillo and Belmonte hatch escape plans, but in order to carry them out they must first take on the two stronger men.
The Pasha and Osmin are not willing to give up the women. In their despair, they seek to assert their claim to the women by force. After a long battle, the power balance is re-structured.