Online:Pulled Under

Quick Walkthrough
# Talk to Bonohild Windtorn
# Help Yiri find her voice.
# Talk to Centurion Andrin. 
# Uncover the Worm Cult plot.
# Kill Anchorite Garmar.
# Talk to Centurion Andrin.

Detailed Walkthrough
Continue talking to Captain Viveka to start this quest.
:''"I already owe you. But I'm hearing rumors. They need to be investigated."
:What would you have me do?
:"My cousin, on my pa's side. Her father's missing, and the family says Yiri saw what happened. Problem is, he went missing during the attack. But he wasn't anywhere near the west wall."
:What did she say happened?
:"She swears something pulled him into the canals. Poor thing's shocked out of her gourd. As you can see, I'm a little occupied. Get Yiri talking. Tell the Pact's commander, Centurion Andrin, what you learn."''

Yiri's home, Windtorn House, is close to the canal. Inside, you need to talk to Bonohild Windtorn upstairs. She says someone just tried to kill her niece, and you note that he is a Worm Cultist. 

You examine the cultist's body and find a note, Or Else. Read the note, then talk to Yiri and Bonohild. However, Yiri is unintelligible. You can intimidate her, if you have the perk, or you will have to calm her down before you can talk to her. Talking to Bonohild reveals that a cup of Densorr's smelly tea might calm her down. You should ask J'darzi, a Khajiit trader, if he has white moon tea. She warns you that it won't be cheap.

Yiri reveals that a dead thing in the water ate her father. She is afraid it will get her too.

Report your findings to the Centurion. 
:"Are you a Jarl, General, or a member of the gods-cursed Tribunal? No? Then shove off!"
:There are zombies in Riften, Centurion. The Worm Cult is among us.
:''"This again? Look, the cult is gone. I was dispatched to the city with all of five soldiers. The rest marched off after the giant. I don't have the manpower to investigate rumors."
:I can investigate, then.'''

He thinks you're wasting your time, but lets you go ahead. He suggests checking the east side of the city, and you can ask him why he doesn't care about the people. He dismisses this and replies that he's been busy and doesn't have the time to chase down rumors.

Worm Cult Plot
You need to talk to a homeless citizen in the eastern part of Riften. A zombie appears, and you must kill it to progress. Loot it for clues, then head north to search the stables. In one of the stalls is a lump of pig iron. You need to search the smithy for clues now. The smithy is to the west. Behind the smithy is a fish rack and an injured citizen named Sirilu Tharam. Talk to her, or search the fish rack. If you talk to her, she says a zombie jumped out of the lake and attacked her. It's attracted to the fish. The zombie reappears; defeat it and loot it to find the next clue. Now you need to continue west to the docks.     

Anchorite Garmar is at the very end of the docks. Defeat him, then talk to the Centurion. 
:'''The Worm Cult was here. I've pushed them out of Riften, but they left with a shard of Wuuthrad.
:"A shard of Wuuthrad. Here? You must be joking. The Worm Cult is a danger to us all. Though, from the look on your face, I can see you're not. We'll double patrols with the five men we have. In the meantime, thank you for running them out of town."''
  

Quest Stages