Grimoaldo has usurped the throne and forced King Bertarido to escape to Milan. Bertarido’s wife and son are left behind. Gramoaldo decides to break off his engagement with Enduige and instead marry Rodelinda. Meanwhile, Bertarido returns to Milan in disguise with the help of his friend, Unulfo. Unfortunately, Bertarido is captured and matters are further complicated by the machinations of Garibaldo, who also loves Eduige and desires to become king himself. With the assistance of Unolfo, Bertarido escapes from prison, kills Garibaldo, pardons Grimoaldo and is restored to the throne.