Pearls Before Swine

You can acquire this sidequest by talking with the guard captain in Denerim's market district.

Fast-Travel to the newly-opened area in Denerim, have a word with the armed men there. You can either intimidate them away, or fight them there. Keep in mind, that whichever route you pursue, when you fast-travel again, you will be interrupted by the guard Captain, and a group of angry mercenaries. It's not too difficult a battle, but there are several foes to engage in at once.