Kurwenal now appears and says that Tristan has agreed after all to see Isolde. When he arrives, Isolde tells him that she now knows that he was Tantris, and that he owes her his life. Tristan agrees to drink the potion, now prepared by Brangaene, even though he knows it may kill him. As he drinks, Isolde snatches the rest of the potion from him and drinks it herself. They both believe they are about to die, and they declare their love for one other. Kurwenal comes and says that King Marke is arriving. Isolde asks Brangaene which potion she prepared and is told that it was not the death poison, but a love-potion. Outside, the sailors welcome the arrival of King Marke.