Prime Suspect

Prime Suspect is an Act 2 main quest in Dragon Age II.

Acquisition
This quest is acquired by completing the main quest Finding Home. Speaking with Aveline will prompt her to ask you to keep Emeric quiet, as his relentless investigation into the deaths of young women (which was covered in Act 1 as The First Sacrifice) has caused the city guard to embarrass itself. Speaking to Emeric will continue the quest.

If you accept the quest along a Humorous line of conversation:

If you accept the quest by beginning the conversation with an Aggressive or Humorous tone, but end Diplomatic:. After the second Humorous/Aggressive response, Sebastian will chime in that "this is a worthy cause." Selecting the Diplomatic option at this point accepts the quest and grants Sebastian's approval.


 * Bug: Investigating during conversation prevents approval gain from Sebastian. (v1.02, PC)

You will have to accept the quest either way, but if you choose an Aggressive response to end the conversation: ,

Walkthrough
Go to The Gallows to speak with Emeric, and he will ask you to go to Gascard DuPuis' estate in Hightown to find evidence of his guilt as the murder of the young women. If you agree and go to the house you will find the place full of shades and other enemies. There will be a note on the table in the first room, thanking DuPuis for the last "shipment" (likely one of the female victims) and saying an artifact is on the way as payment (not seen on screen, but presumably the source of all the creatures infesting the mansion). When you enter the final room you will find Gascard DuPuis with an obviously abused and terrified woman named Alessa. He claims to be the one that has been hunting the murderer, although he admits to resorting to blood magic in order to do it. You can either fight him or let him go.

if you choose the humor choice of "This I have to hear." in this conversation.

Whether you fight him or let him go, when you go to tell Emeric what happened there will be a Templar named Moira telling you that Emeric is ready to meet you tonight according to the note you gave him. Of course you didn't give him a note at all, it looks like a trap. When you arrive at the back alley where you told him to "meet" you there will be shades and abominations and a dead Emeric. The templar you spoke to earlier will arrive after the battle. Moira (the templar officer) will tell you there is a dangerous mage about that Meredith will want captured and run off. The follow up quest is All That Remains which is acquired later in Act 2 from Hawke Estate.
 * You can tell her you killed Gascard. As he wasn't the culprit, the only storyline impact is the restriction imposed in the later quest, All That Remains.
 * If you did not kill Gascard you can either implicate him in which case the Templar tells you she will inform the city guard and Gascard DuPuis will not escape the city alive. Or clear him and she will say that they will have to continue investigation that Emeric started, considering he was right and died for it.
 * Implicating Gascard may lead to his execution, off-screen, by the Templars. This restricts your options for completing the following quest, All That Remains.

Result
If you allow DuPuis to live:, , ,. Surprisingly, Sebastian doesn't seem to mind. (NOTE: needs confirmation. As of 05/14/11 PC version does not award rivalry points to Fenris or Merrill. Possible bug. May also be attributed to if the party member in question has been romanced.)

As always, once a companion reaches maximum friendship, no approval is gained or lost from later events. Drops Gascard DuPuis's Favorite Hat.

Rewards
The XP payout is in the 1300-1600 range. You gain roughly 1900 more exp if you decided to kill DePuis from the fighting in his mansion.

Bug

 * This occurs in the room where you first meet Gascard. If you have a rogue in your party that performs a Backstab talent on any Shade at the edge of the terrace, he or she may appear at the courtyard, down below (since he/she went at the back of the Shade).