There is a rush toward the bank and a great shout of acclaim, as the swan with a graceful sweep rounds a bend in the river and brings the shell-like boat, in which stands a knight in dazzling armour and of noble mien, up to the shore. Not daring to trust her senses and turn to behold the wondrous spectacle, Elsa gazes in rapture heavenward, while Ortrud and Telramund, their fell intrigue suddenly halted by a marvel that surpasses their comprehension, regard each other with mingled amazement and alarm.
A strange feeling of awe overcomes the assembly, and the tumult with which the advent of the knight has been hailed dies away to breathless silence, as he extends his hand and in tender accents bids farewell to the swan, which gently inclines its head and then glides away with the boat, vanishing as it had come. There is a chorus, in which, in half-hushed voices, the crowd gives expression to the mystery of the scene. Then the men fall back and the Knight of the Swan, for a silver swan surmounts his helmet and is blazoned upon his shield, having made due obeisance to the King, advances to where Elsa stands and, resting his eyes upon her pure and radiant beauty, questions her.
"Elsa, if I become your champion and right the foul wrong that is sought to be put upon you, will you confide your future to me; will you become my bride?"
"My guardian, my defender!" she exclaims ecstatically. "All that I have, all that I am, is yours!"
"Elsa," he says slowly, as if wishing her to weigh every word, "if I champion your cause and take you to wife, there is one promise I must exact: Never must you ask me whence I come or what my name."
"I promise," she answers, serenely meeting his warning look. He repeats the warning and again she promises to observe it.
"Elsa, I love you!" he exclaims, as he clasps her in his arms. Then addressing the King he proclaims his readiness to defend her innocence in trial by combat.
In this scene occurs one of the significant themes of the opera, the motive of warning—for it is Elsa's disregard of it and the breaking of her promise that brings her happiness to an end.
