Lady Hannah is a noble located on the west side of Baldur's Gate Central who will inform the party about Ragefast enslaving a nymph while voicing her displeasure with men in general. If you agree to help, she will give you The Captive Nymph quest.
There ought to be a law to keep lecherous old men like Ragefast off the streets!
Ragefast! Oh, he makes me seethe! He's a mage on a power trip and what does he do? He acquires his own personal nymph and enslaves her in his quarters! Men are callous brutes and, personally, I wish the world were rid of them.
Oh, good. This world still has some honor left. His house is in the northwest part of town. I wish you luck and all the passion of my fury in your task.