The Raid

Step 1: Find Wujeeta in the Riften Docks/Fishery. During the day she is outside by the boats, although sometimes in the fishery itself. Talk to her and give her a health potion when prompted. talk about the skooma trade and she'll point you to the jarl. She also tells you that the only person who has the keys to the warehouse are Bolli, and the Jarl herself.

Step 2: Speak with the Jarl. The jarl will tell you that it's been nearly impossible to stop the skooma trade, but offers you a try and hands you the key to the warehouse.

Step 3: Enter the warehouse and eliminate Sarthis. Upon entering, Sarthis and his bodyguard attack you. Kill them both. Head down to the basement and hang a left. Inside is a ton of skooma, moonsugar, and more importantly, the satchel. Open the satchel and grab the shipment papers. Read them. Head back to the Jarl.

Step 4: Finish the quest by giving the shipment papers to the Jarl and she thanks you heftily.