’I give thee thanks, my faithful swan. 
    Turn thee again and breast the tide;
    Return unto that land of dawn
    Where joyous we did long abide. 
    Well thy appointed task is done. 
    Farewell, my trusty swan.’

Then, while the swan slowly sails down the river and out of sight, the Swan Knight announces to the king that he has come as Elsa’s champion, and, turning to her, asks whether she will be his wife if he proves victorious.  Elsa gladly promises him her hand, nor does she even offer to withdraw this promise when he tells her that she must trust him entirely, and never ask who he is or whence he comes:—­

   ’Say, dost thou understand me? 
    Never, as thou dost love me,
    Aught shall to question move thee
    From whence to thee I came,
    Or what my race and name.’

Elsa faithfully promises to remember all these injunctions, and bids him do battle for her, whereupon he challenges Telramund, with whom he begins fighting at a given signal.  The Swan Knight soon defeats his enemy, who is thus convicted of perjury by the judgment of God, but he magnanimously refuses to take his life.

Then, turning to Elsa, who thanks him passionately for saving her, he clasps her in his arms, while Telramund and Ortrud, his wife, bewail their disgrace, for, according to the law of the land, they are doomed to poverty and exile.  Their sorrow, however, is quite unheeded by the enthusiastic spectators, who set Elsa and Lohengrin upon their shields, and then bear them off in triumph, to the glad accompaniment of martial strains:—­

   ’Chorus.

        We sing to thee,—­we praise thee,
        To highest honour raise thee. 
        Stranger, we here greet thee delighted. 
        Wrong thou hast righted;
        We gladly greet thee here. 
    Thee, thee we sing alone.  Thy name shall live in story. 
    Oh, never will be one to rival thee in glory!’

It is night when the curtain rises upon the second act; the knights are still revelling in the part of the palace they occupy, while the women’s apartments are dark and still.  The street is deserted, and on the steps of the cathedral sit Frederick and Ortrud, who have been despoiled of their rich garments, and are now clad like beggars.

Frederick, who feels his disgrace, bitterly reproaches his wife for having blasted his career, and seeks to induce her to depart with him ere day breaks; but Ortrud refuses to go.  She is not yet conquered, and passionately bids him rouse himself, and listen to her plan, if he would recover his honour, retrieve his fortunes, and avenge himself for his public defeat.  She first persuades him that the Swan Knight won the victory by magic arts only, which was an unpardonable offence, and then declares that, if Elsa could only be prevailed upon to disobey her champion’s injunctions and ask his name, the spell which protects him would soon be broken, and he would soon become their prey.