1. Enter the hanged man during the daytime and talk to the drunken templar, Ser Roderick, immediately on your left as you go in, proceeding with the appropriate dialogue options. The templar will leave with the intention of reporting your erroneous claims.
2. Go to the gallows. Look for the harbormaster's assistant on the right. In the stall behind him is a scroll. Read the scroll and scribble down the templar's name. Take the scroll to the dockworker across the courtyard and speak with him.
3. Head to the docks. Speak to Mistress Selby for a reward.
http://dragonage.wikia.com/wiki/How_to_Frame_a_Templar
