Romeo and Juliet in Scotland. That is the easiest way to sum up Gaetano Donizetti's dramatic opera, Lucia di Lammermoor.
It is, perhaps, unfair to summarize this opera so succinctly, when it is so famous, so much a "classic" of the opera genre. Following the links on Wikipedia, I learned that Lucia was based on a Waverly novel by Sir Walter Scott - The Bride of Lammermoor - which in turn was apparently based on true events. That might explain why it is somewhat more credible, and more compelling, than Romeo and Juliet, even though the plot runs nearly parallel.
The Ashton family is archenemies with the Ravenswood family (what a splendid name!). As these things go, Lucia Ashton (Anna Netrebko) falls in love with Edgardo Ravenswood (Piotr Beczala). She happens to have a brother, Enrico (Mariusz Kwiecien), and because he is a baritone, we know whose side he's not on. Taking her love for Edgardo as a betrayal, Enrico schemes to force his sister into a marriage to Lord Arturo Bucklaw, a political ally. It does not get better from there.