S1·E17 Jorinde and Joringel

When Jorinde and her fiancé Joringel visit the woods, its witch they unknowingly encountered earlier draws them to her home and turns Jorinde into a nightingale and takes her as she does every maid she meets. After being unable to move to stop it, Joringel is driven out of the woods by her magic with only a puzzling message from Jorinde, and can't see a way to best the magic to free her.