Fools Rush In
You get this quest from Isabella at the Hanged Man after completing the Tranquility quest. Agree to help her, then go meet her at Hightown at night. After the combat, loot one of the bodies to find Hayden's letter, then follow Isabella to the Chantry, fighting more raiders along the way. Enter the Chantry and talk to Hayden, leading to inevitable combat. Once you defeat Hayden, the quest is completed and you unlock Isabella as a companion.
Isabella's Contact
This quest starts when you complete Fools Rush In. Head to the Hanged man and talk to Isabella. This completes the quest, and also starts a new quest: Finders Keepers.
Finders Keepers
After talking to Isabela, go to Martin's room in the Hanged Man to see what help he needs. Then go to the Docks during the day. Talk to the Longshoreman and the Harbormaster, and then to Aden. Bribe Aden to get the location of the cargo. Then go to Woodrow's warehouse. on the eastern edge of the docks. Defeat the guards in the entrance and enter the warehouse. Follow the waymark to the chest, defeating enemies along the way There are traps here, so its best to have a rogue lead the way. Then return to Martin. Reveal where his cargo is to unlock his poison shop.
Secret Rendezvous
Talk to the Suspicious Lady in the Hanged Man. Then travel to the warehouse district of the Docks (at night). Sneak around and climb the stairs, standing on the top of the steps to eavesdrop on the conversation, and when they notice you a combat ensues. After you defeat all the enemies. return to the suspicious lady at the Hanged Man.
Terror on the Coast
You get this quest if you imported a save file in which you played Warden's Keep and spared Sophia Dryden. Head west on Wounded Coast to encounter some spiders, then go further west to locate Sophia.
The Conspirators
You get this quest only if using an imported Dragon Age Origins file with the Silver Order formed and Vigil's Keep was saved. Go to the Hanged Man area and talk to Joanna. Then go kill Amaratnthine conspirators in four locations: Hightown, The Docks, Blooming Rose, and Sundermount. Go back to Lowtown and talk to Joanna to conclude the quest.