After Thancred expresses his suspicion of Sister Ourcen, Isembard seeks to clear her name by having you investigate at the Golden Bazaar.
This quest is available if you have completed the quest A Proper Burial, and have reached level 19.
Starting the Quest
Talk to Isembard in Camp Drybone in Eastern Thanalan to start the quest.
Speak with the Uncombed Urchin
Go east from Isembard and go through the archway, then follow the road. When the road splits, follow it northwest, then west. It will lead you to the Golden Bazaar. You can talk to the Chocobokeep there to add the Golden Bazaar to your list of Chocobo Porter destinations.
Go to the northwest corner of the town and talk to the Uncombed Urchin.
Save Sister Ourcen
Go east and you will find Ourcen in a purple circle. When you walk into it, a Rotting Mage and Rotting Pikeman appear. Kill the Mage first, then the Pikeman. After they are dead(er), talk to Ourcen.
Report to Isembard
The path to the east is more dangerous, so you may wish to go west and follow the path from there to Camp Drybone. Talk to Isembard to complete the quest.
Next Main Scenario Quest
After you complete the quest, talk to Isembard to accept the next quest: Amalj'aa Wrong Places.