Based on the legend of Tristan and Isolda, Wagner's 'Tristan und Isolde' has long been acknowledged as the beginning of musical modernism. It is said that the entire opera is an attempt to resolve the tension set established in the first eight bars.
In the story, Isolde plots to kill Tristan, the man who is taking her to be betrothed to King Marke of Cornwall. She deeply resents him as she had nursed him back to health after a battle only to find he was the slayer of her fiancé Morold. Isolde asks her companion Brangäne to prepare a potion that will cause death, but instead she brews a love-potion. Both drink it and fall hopelessly for each other. They continue their affair when they reach Cornwall, but are spied on by Mark’s man Melot who wounds Tristan. Tended by Kurwenal, he holds onto life just long enough for Isolde to reach him, then falls and dies. As Isolde stands stricken by grief, Marke and Melot arrive to pardon the lovers but Kurwenal does not believe this, kills Melot and is himself killed. Isolde feels Tristan calling to her from the ‘realm of night’ and even as Brangäne tries to persuade her to live, falls dead next to him.