The 67 year old Leoš Janáček wrote this opera out of love for Kamila Stösslová, a woman he met four years earlier in a resort. The vacation love was almost forty years longer, but it didn’t stop him from dedicating this work to her. In that light the material is a bit disturbing I think.
The opera tells about the love of the married Káťa for Boris, who lives at the adjoining estate. Tichon, the husband of Káťa is away for a while, and she is, well… not very faithful in her mind. The two meet and confess their secret to each other. But now the trouble is starting for real of course.
Ten days later Káťa is upset because of what happened. She confesses her love, but immediately afterward regrets having done so: she has put herself, but also Boris in an impossible position. And since this is opera, she throws herself into the water and drowns.
What is the great composer saying to the young girl he met? He wants her to find an example in this story? His own wife had committed suicide in 1916 because of his adultery with a singer in Prague.
For the rest of his life he would be totally devoted to Kamila, writing 730 letters to her. That love was totally one sided, alas for Janáček.