(German: Der Protagonist)
One act opera by Georg Kaiser and Kurt Weill (1924/1925)

Story line
A troupe of traveling English actors in Shakespeare's time rehearses a comic pantomime. Their leader, the Protagonist, meets with his sister, who fearfully informs him that she has taken a lover. To her surprise, he is not offended, she says she will bring her lover to meet him.
When the group hears that a bishop will visit the play, the Protagonist directs his troupe to play the same pantomime but with a tragic twist. As they rehearse, his sister returns with her lover. The Protagonist, caught up in the play stabs her to death: He requests that he not be arrested until after the performance, because he is playing his best role in life.

Georg Kaiser, impressed by Weill's theatrical essay and pantomime Die Zaubernacht The Magic Night, allowed the composer to use his play The Protagonist (1920) for a larger pantomime-like opera.

Source:
The Kurt Weill Foundation
Jurgen Schebera - Kurt Weil a Biography