While searching for the missing Ninette de Carrac, Hawke meets a templar by the name of Emeric who is investigating the mystery of women disappearing throughout the city. While following a lead to the Dark Foundry in Lowtown, Hawke catches a glimpse of Quentin before he flees.
Three years later, Hawke is lead to investigate a nobleman named Gascard DuPuis. In DuPuis's mansion, Hawke meets Gascard again, who claims to also be searching for the killer because he murdered Gascard's sister. A letter from the First Enchanter of the Starkhaven Circle of Magi to Gascard DuPuis suggests that Quentin may have been one of its escaped mages that fled after the Circle was burned down. Hawke may opt to kill Gascard or to let him go.
Upon returning home, Hawke finds that their mother has gone missing. If Gascard is still alive, Hawke can ask him to find Leandra using blood magic in Darktown, or head out to Lowtown to search for her with Gamlen's aid. A street urchin reports that he saw a wounded man ask Leandra for help, and that Leandra followed him. A trail of blood leads back to the foundry and reveals a hidden entrance to an underground lair that contains multiple female corpses. Eventually, Hawke finds Quentin and Leandra.
Driven insane by the death of his wife, Quentin kidnapped, murdered, and dismembered several women in order to take those parts of each that he could use to rebuild the likeness of his beloved. Leandra was to provide the semblance of his beloved's face. Finding their mother near death, Hawke kills Quentin and the undead, Abominations, and Shades he summons; including several desire demons which had possessed Quentin's victims.
If Hawke takes Gascard with them to find Quentin, it is revealed that Gascard is actually Quentin's pupil looking for the secrets of necromancy, and the story he told of his sister is a lie. Quentin originally promised to teach Gascard but had forsaken that promise after being paralyzed by his wife's death. Gascard and Quentin reconcile and Gascard joins Quentin to fight Hawke. However an aggressive or diplomatic Hawke can persuade Gascard to turn on his mentor, while if Varric is in the party, Gascard is killed by him before Hawke can act.
Quentin and his creatures are killed and Leandra dies in Hawke's arms.During the search, letters show that Quentin entertained correspondence with a certain "O". "O" also supplied him with dangerous, presumably illegal literature he needed to complete his necromantic ritual. During the final moments of the Templar-Mage conflict in Kirkwall, it is revealed that First Enchanter Orsino knew about Quentin's research.