The scene opens on Sister Corrina Sundwall, who has been tasked with bringing the Chant to Orzammar. The assignment is meant as a punishment - she's been arguing with her Revered Mother in Val Royeaux, advocating to allow elves, dwarves, and qunari to become sister and brothers of the Chantry or Templars. She thinks the Chant should be accessible to everyone, and that anyone who wants to devote their lives to it should be able to. Revered Mother does not agree, and so it's off to the caves for Corrinna. Corrinna, however, is not planning to let this stop her. She's determined to show everybody in Val Royeaux that there are non-humans who need the Chant.
So she shows up in Orzammar, and she goes straight to where she thinks the message and charity of Andraste are needed the most: Dust Town. This is where we find out that Sister Corrina wasn't always a sister...once upon a time, she was a chevalier, and she's still got the skills to take out a few dusters who think they're going to impede her mission. It's when she's proven herself with a blade that Dust Town begins to respect her, and that a young woman with Carta connections begs her for help: please, please go into the Deep Roads and find my idiot brother. She agrees...and that's where the adventure begins.