From Royal Opera House website:
The dashing corsair Simon Boccanegra and Maria, daughter of the nobleman Jacopo Fiesco, have fallen in love and had an illegitimate daughter. The child has disappeared from her foster-home. Boccanegra returns to Genoa to break the news to Maria, and learns of her death as a crowd, led by the plebeian Paolo Albiani, proclaim him Doge of Genoa.
Twenty-five years later, Boccanegra meets an orphaned woman called Amelia Grimaldi, and discovers that she is his long-lost daughter. Father and daughter are overjoyed to find each other - but their happiness is short-lived. Genoese aristocrats, including Amelia's lover Gabriele Adorno, are planning a rebellion, and Boccanegra's own advisor Paolo has turned against him…