Portrait of the Past is an Act 1 companion quest for Bethany Hawke in Dragon Age II.
Acquisition
To be able to get this quest, Bethany must have survived the Prologue. While on the quest Birthright, Hawke will find an old betrothal portrait of Mother in one of the chests in Amell Estate Cellar, triggering the quest.
Walkthrough
After completing the Birthright, talk to Bethany and give her the portrait. Regardless of dialogue choices, Hawke will earn 
Bethany: friendship (+15).