This quest is automatically acquired upon completion of On the Loose.
Speak to Varric at The Hanged Man tavern in Lowtown. Varric reveals that he sold Bartrand's mansion in Hightown sight unseen, but now the new owners believe the property is haunted. Varric suspects that the lyrium idol is still there, or, if Family Matter was refused or never accepted, Varric suspects a non-specific relic is to blame. He asks Hawke to accompany him and investigate the mansion, believing that because Hawke is a mage or comes from a family of mages, Hawke is adept in dealing with "weird."
Agreeing to help Varric along a diplomatic or humorous path results in Varric: friendship (+25). Agreeing to help Varric along an aggressive path results in (+10) Refusing to help Varric along a diplomatic or humorous path results in Varric: friendship (+10) Refusing to help Varric along an aggressive path results in (+30).
A new companion quest Haunted is unlocked even if Hawke decides not to help Varric.