A forest near the castle of the Grail
Amfortas, the custodian of the grail, has been seduced by Kundry and wounded by Klingsor. The wound remains unhealed; no herbs do more than briefly alleviate the pain, as does bathing in the holy lake. Amfortas and the knights of the grail hope for the advent of the promised healer, a pure fool, made wise by pity. The squires abuse the strange, wild woman, Kundry, and Gurnemanz, the oldest of the grail knights - not knowing that it was she who was responsible for Amfortas' wound - reproves them for their lack of charity; she may be, as they say, accursed, but she now lives under the protection of the grail. She was found almost lifeless in that place by Titurel, father of Amfortas, when he built the grail castle of Monsalvat.
Gurnemanz tells how angels brought the grail and spear to Titurel, to be guarded only by the pure in heart. Klingsor, although aspiring to the grail, was sinful and his self-castration made it impossible for him to serve the grail, though it did give him magic powers, which enabled him to transform the wilderness into a luxuriant garden in which beautiful women ensnared the knights. Parsifal is brought in carrying his bow and arrows, having killed a swan. He does not know who his father was, or even his own name, only that of his mother. Kundry explains that his mother had tried to bring him up cut off from the world, to save him from being killed in battle like his father. He remembers having seen knights and followed them and Kundry tells him that his mother had then died of grief. Hoping that Parsifal may prove to be the pure fool of the prophecy, Gurnemanz takes him to the castle, as the scene changes around them. The covered grail is carried before Amfortas and the voice of Titurel, entombed in the wall, is heard demanding that Amfortas unveil it and allow its powers of renewal to sustain him, but these powers also prolong Amfortas' life and suffering. He obeys reluctantly and blesses bread and wine which are distributed among the knights. Titurel is refreshed, but Amfortas suffers. Parsifal, who has watched in silent pity, is chased away angrily by Gurnemanz for not having understood anything of what he has seen.
Klingsor's magic castle
Klingsor summons Kundry and orders her to seduce Parsifal. He derides her for clinging to the knights of the grail, as if to atone for the wrong she has done them. Klingsor hopes soon to possess the grail himself. He summons his knights to defend the castle against Parsifal, but laughs when they are defeated.
His tower disappears, replaced by a magic garden, in which girls lament their lovers' wounds and reproach Parsifal. Enchanted by their loveliness, he offers to play with them and they throng around him with a different kind of play in mind, until they are driven off by Kundry, now transformed into a beautiful woman.
She calls Parsifal by his name and gains his confidence by relating how she had known him in his childhood, reminding him of his mother's love and death, going on to describe his father's love for her and to promise him similar delights, kissing him passionately. At once he feels the pain of Amfortas' wound and realises that Kundry had seduced Amfortas. He is also consumed with guilt for his own youthful folly. He recoils from Kundry, who reproaches him with feeling for the sufferings of others, but not for hers, relating how she had laughed at Christ, begging him to bring her redemption by yielding to her; but he explains that her salvation will only be ensured by his refusal.
She curses him to a life of wandering like her own and calls on Klingsor for help. He appears on the tower, throwing the spear at Parsifal, who seizes it and makes the sign of the Cross, causing the tower to crumble and the garden to wither.
Pleasant spring landscape in the domain of the grail
Gurnemanz, now old and grey, is living as a hermit. He finds Kundry, almost lifeless in a thicket and no longer wild. Parsifal returns, incurring Gurnemanz's reproaches (before he recognises him) for being armed on Good Friday. With joy he recognises Parsifal and the spear, and Parsifal explains that he has found his way back through great suffering to relieve the torment of Amfortas.
Amfortas has refused to unveil the grail, so Titurel, deprived of its life-prolonging refreshment, has died. Parsifal's guilt weighs heavily on him and he seems about to faint, but Kundry brings water. She washes his feet and Gurnemanz bathes his head. Parsifal baptises Kundry and Gurnemanz leads him to the grail castle, as the scene gradually changes. The knights carry the body of Titurel and call on the unwilling Amfortas to unveil the grail once more. Parsifal cures him with a touch of the spear and unveils the grail, of which he is now the ruler, as the knights rejoice and Kundry falls lifeless.