Hilda has come to bid her fountain good-night, and Florian is overwhelmed by her beauty in the moonlight. She tells it of the love she had lost: a certain Prince Florian, but how it (so far as it could) has taken his place in her heart. Florian then speaks through the fountain, telling her he loves her, but wondering what she would do if this Prince Florian should be alive after all. She tell him (as the fountain) that it would be an unbearable, but impossible joy: he (the fountain) should be content for she has pledged herself to him forever. But neither of them realise that Mousta has overheard this vow.