The Cornish knight is escorting the captured Irish princess to be the bride of his uncle. To make matters worse, the Cornish knight killed the princess’ husband-to-be in combat. And on top of that, the princess nursed the Cornish knight after the battle — before she knew he had done in her betrothed. The Irish princess, as you might imagine, is by now majorly ticked.

So she orders her maid to prepare a poisonous potion, then confronts the Cornish knight, demanding satisfaction for her fiancé’s death. The Cornish knight offers her his sword, but the princess suggests instead that they drink in peace. They each sip from the potion of death mixed by the princess’ maid. But aha! The maid has a mind of her own. Instead of a phial of poison, she has mixed them a love potion. The Irish princess and the Cornish knight fall madly into each other’s arms.

Richard Wagner took the tale of Tristan and Isolde from legend. The resulting opera debuted in 1865 at Munich’s Royal Court Theater. It’s a sweeping, romantic story, and it gets worse. The snippet above is merely the setup.

The Metropolitan Opera will broadcast the lengthy work on March 21 at 8 p.m. on PBS-TV with an audio simulcast on WCVE-FM. Ben Heppner and Jane Eaglen star as the Cornish knight Tristan and the Irish princess Isolde. Katarina Dalayman is Isolde’s maid Brang„ne, Hans-Joachim Ketelsen is Tristan’s servant Kurwenal and René Pape is Tristan’s uncle King Marke. James Levine conducts. The four-hour opera, sung in German with English subtitles, was taped at the Metropolitan Opera House in December 1999. Garrick Utley