Night Lies

Night Lies, Sharp Little Pinpricks, and Pier Pressure make up the unnamed Cleaning up the Streets collection of side quests in Act 1 (pre-Expedition into the Deep Roads) of Dragon Age II.

Acquisition
The Guardsman Pretenders are all over Hightown. You may need to leave the area and come back to spawn other groups but the main idea is to kill ALL Guardsman Pretenders in the area to acquire this quest. After defeating several waves of Guardsman Pretender enemies in Hightown at night you will receive the following message that initiates this quest.

The Shallowguard use guardsmen uniforms to get close to their victims. Assault their storehouse, and take out the false captain.

Walkthrough
Enter "the Barracks" and defeat the Guardsman Pretender and "Captain" Qerth". Afterward, return to The Hanged Man and speak to A Friend for your reward.

Result
Defeating "Captain" Qerth" and his Shallowguard troops gives you Palvo's Cocksure Cleaver, Formari Work Boots and other minor loot.

Rewards

 * 2
 * 500 XP.

Bugs

 * It's been reported (but not confirmed) that some people were unable to complete this quest after beginning Isabella's side quests.