Act I
Princess Isolde of Ireland is sailing towards the Corn 6all on Tristan's barge, as his uncle, King Mark, plans to marry her. The sailors taunt her with a song about an Irish young woman and her maid, Brang Animkne, tries to calm her down. Isolde questions Tristan, but he deftly evades her inquiries. His sidekick, Kur 6angenal, taunts Irish women loudly and sings a tongue-in-cheek song about Isolde's fiance, Morold, who was killed by Tristan when he sailed to corn 6angall to avenge Ireland. Izolda barely tames her anger and reveals to Brang the light how a wounded Tristan came to her disguised after a duel with Morold to heal him with her knowledge of herbs and Magic learned from her mother. Of course, she recognized Tristan, but her determination to avenge Morold's death dissipated when he begrudgingly looked into her eyes. She now regrets immensely her hesitation that she did not kill him and wishes death for him as well as for herself. Brang animkne reminds her that it is not dishonorable to marry a king and that Tristan is simply doing his duty. Isolde continues to feel that his behavior reveals his aversion to her and instructs Brang Animgne to prepare her mother's death potion. The two are ordered to leave the deck by Kur 6enal when the scouts see land. Isolde insists that she will not go with Tristan until he apologizes to her. He only coldly greets her and this enrages her to demand satisfaction for Morold's death. Tristan offers her his sword, but is unable to kill him. Instead, Isolde suggests making a toast as a sign of reconciliation. Tristan knows he plans to poison them both, but he drinks the drink anyway, and so does she. Instead of the onset of death, they exchange a loving look, and then fall into each other's arms. Brang admits to the man that she has brewed the love potion, and the voices of the sailors announce their arrival at the Corn of the man.
II. Action
Isolde waits impatiently in the garden of Mark's Castle for a meeting with Tristan, and meanwhile, in the distance, brass instruments announce the King's departure to hunt. Isolde thinks the hunting expedition is far away, but Brang is warned against spies, especially the jealous Knight Melot, whom she caught watching Tristan. Isolde tells her that Melot is Tristan's friend and sends her to watch, lighting a warning torch. When Tristan arrives, she greets him passionately. Thanks to the darkness, it obscures the light of conventionality and false facades and both feel safe in the embrace of the night. Brang's distant voice warns them that it will soon be Dawn, but the lovers are deaf to the danger and compare the night to the death that will one day unite them. Suddenly, Kur Khumentenal rushes in with the news that the king and his companions have returned. They are led by Melot, who unmasks the lovers. King Mark is stunned that Tristan has urged him to marry and chose this bride. He cannot understand how he could be so dishonored by someone so close to him. Tristan does not find words in response. He asks Isolde if she will follow him to the kingdom of death. As she clings to him, Melot attacks Tristan, who, wounded, falls into Kur 6tenal's arms.
III. Action
The mortally wounded Tristan is back at his castle, watched over by Kur 6tenal. The shepherd inquires after the master, and Kur 6thenal explains that only Isolde could save him with her magical abilities of ranocellanism. The shepherd agrees to play an over-the-top tune on the pipe as he watches an approaching ship. Tristan is delusional about the kingdom of the night, where he will return with Isolde. He thanks Kur 6tenal for his adherence, then imagines that Isolde's ship is approaching. Unfortunately, the shepherd's languid chant announces that the sea is still empty. Tristan remembers a childhood melody that reminds him of a duel with Morold. He wishes Isolde lek to finish him off instead of having to suffer now. The shepherd's chant cheers up at last. Upset, Tristan gets out of his hospital bed and tears off his bandages to bleed his wounds. Isolde rushes into the room, and Tristan collapses, dying, into her embrace. The shepherd announces the arrival of another ship, and the Kur 6tenal assumes that Marke and Melot are coming, so he barricades the door. From the outside, Brang's voice can be heard trying to calm Kur 6tenal, but he refuses to listen to her and stabs Melot, and then the King's soldiers finish him off. The King of Marche is heartbroken at the sight of the dead Tristan, and Brang Animkne explains to ISOLDE that the King has come to pardon them. Isolde is distracted and does not hear her; Tristan's vision invites her into the other world, and she collapses dead on his corpse.
I. DEJANJE
Irska princesa Izolda pluje proti Cornwallu na Tristanovi barki, saj se njegov stric, kralj Mark, namerava poročiti z njo. Mornarji se ji rogajo s pesmijo o irski mladenki in njena služkinja Brangäne jo poskuša pomiriti. Izolda izprašuje Tristana, a on se spretno izmika njenim poizvedbam. Njegov pajdaš Kurwenal glasno zasmehuje Irke in poje porogljivo pesem o Izoldinem zaročencu Moroldu, ki ga je Tristan ubil, ko je priplul v Cornwall, da se maščuje za Irsko. Izolda komaj kroti svojo jezo in razkrije Brangäne, kako je ranjeni Tristan po dvoboju z Moroldom zakrinkan prišel k njej, da ga je pozdravila s svojim znanjem zelišč in magije, ki se je naučila od matere. Seveda je prepoznala Tristana, a se je njena odločenost maščevanja za Moroldovo smrt razblinila, ko jo je proseče pogledal v oči. Zdaj neizmerno obžaluje svoje oklevanje, da ga ni ubila in tako zanj kot tudi zase želi smrti. Brangäne jo opomni, da se ni nečastno poročiti s kraljem in da Tristan preprosto vrši svojo dolžnost. Izolda še naprej meni, da njegovo obnašanje razkriva njegov odpor do nje in naroči Brangäne, naj ji pripravi materin smrtni napoj. Kurwenal jima ukaže, naj zapustita krov, ko izvidniki zagledajo kopno. Izolda vztraja, da ne bo šla s Tristanom, dokler se ji ne opraviči. Ta jo le hladno pozdravi in to jo razjari, da zahteva zadoščenje za Moroldovo smrt. Tristan ji ponudi svoj meč, a ga ne more ubiti. Namesto tega Izolda predlaga, da nazdravita v znak sprave. Tristan ve, da ju namerava oba zastrupiti, a vseeno spije pijačo, ona pa prav tako. Namesto nastopa smrti si izmenjata ljubeč pogled, nato pa si padeta v objem. Brangäne prizna, da je zvarila ljubezenski napoj, glasovi mornarjev pa naznanijo prihod v Cornwall.
II. DEJANJE
Izolda nestrpno čaka na vrtu Markovega gradu na sestanek s Tristanom, medtem pa v daljavi trobila oznanjajo kraljevi odhod na lov. Izolda misli, da je lovska odprava daleč proč, a jo Brangäne posvari pred vohuni, še posebej ljubosumnim vitezom Melotom, ki ga je zasačila oprezati za Tristanom. Izolda ji odvrne, da je Melot Tristanov prijatelj, in jo pošlje stražit ter prižge opozorilno baklo. Ko prispe Tristan, ga strastno pozdravi. Zahvaljujeta se temi, da zakriva svetlobo konvencionalnosti in lažnih fasad in se oba počutita varno v objemu noči. Brangänin oddaljen glas ju svari, da se bo kmalu zdanilo, a ljubimca sta gluha za nevarnost in noč primerjata s smrtjo, ki ju bo nekoč združila. Nenadoma prihiti Kurwenal z vestjo, da so se kralj in njegovi spremljevalci vrnili. Vodi jih Melot, ki razkrinka ljubimca. Kralj Mark osuplo besni, da ga je vendar Tristan nagovarjal k poroki in izbral to nevesto. Ne more razumeti, kako bi ga lahko tako onečastil nekdo, ki mu je tako blizu. Tristan ne najde besed v odgovor. Izoldo vpraša, ali mu bo sledila v kraljestvo smrti. Ko mu pritrdi, Melot napade Tristana, ki ranjen pade Kurwenalu v objem.
III. DEJANJE
Smrtno ranjen Tristan je nazaj na svojem gradu, nad njim bdi Kurwenal. Pastir povpraša po gospodarju in Kurwenal pojasni, da bi ga lahko samo Izolda rešila s svojimi magičnimi sposobnostmi ranocelstva. Pastir pristane, da bo zaigral prešerno melodijo na pipe, ko zapazi bližajočo se ladjo. Tristan ima privide o kraljestvu noči, kamor se bo vrnil z Izoldo. Kurwenalu se zahvali za njegovo privrženost, nato pa si predstavlja, da se bliža Izoldina ladja. Žal pastirjev otožni napev sporoča, da je morje še vedno prazno. Tristan se spomni melodije iz otroštva, ki ga spomni na dvoboj z Moroldom. Želi si, da bi ga Izoldin lek pokončal, namesto da mora zdaj trpeti. Pastirjev napev se naposled razvedri. Tristan razburjeno vstane iz bolniške postelje in si strga obveze, da rane zakrvavijo. Izolda prihiti v prostor in Tristan se umirajoč zgrudi v njen objem. Pastir oznani prihod še ene ladje in Kurwenal predpostavlja, da prihajata Marke in Melot, zato zabarikadira vrata. Od zunaj je slišati Brangänin glas, kako poskuša umiriti Kurwenala, ta pa je noče poslušati in zabode Melota, nato pa kraljevi vojaki pokončajo še njega. Kralj Marke je strt od žalosti ob pogledu na mrtvega Tristana, Brangäne pa pojasni Izoldi, da ju je kralj prišel pomilostit. Izolda je zamaknjena in je ne sliši; Tristanov privid jo vabi v oni svet in mrtva se zgrudi na njegovo truplo.