Dragon Age 2 Quest Reference: Act 1 - Secondary Quests - The First Sacrifice
Requirements: Tranquility
You can get this quest from a notice in Hightown. This will lead you to the Hightown Market (day) to speak with Ghyslain de Carrac. He'll tell you that his wife Ninette is missing. Your search will lead you to The Blooming Rose and Jethann. He'll tell you about a templar called Emeric that also asked about Ninette. You'll also find the Stone Toe in his room, which is part of The Paragon's Toe quest.
After you save Emeric in Darktown, he'll explain that he was looking into the disappearances of a few women. Don't ask about helping unless you don't mind losing 5 points with Isabela. Instead say it sounds suspicious, you'll still be able to continue with the continue. Now head over to the Dark Foundry in Lowtown. You'll be attacked as soon you the cutscene ends, so be prepared. Be sure to check behind all doors to find human remains, Ninette's ring and other loot.
Head to the Gallows next to talk to Emeric and show him the remains. You'll get three gold and 250 XP for your trouble. Next you should go to Hightown and Ghyslain to give him Ninette's ring. You'll get the one gold reward either way, but he won't panic if you don't tell him where you found it.