Just like the last quest, The Butcher of Cidaris, this quest will unlock after you talk to Dethmold in the Conspiracy Theory quest. It won’t be necessary for you to complete both of these missions in order to proceed with the story, but at least one of them must be completed in order for you to have enough intel on the rumored uprising to satisfy Dethmold. Competing both is probably the best route, though, because you will get double the experience points before continuing on with the story. The guide for the Butcher of Cidaris quest can be found just prior to this guide.
You will begin this mission in the center of Henselt’s camp, near the three soldiers. They will be drunkenly hollering for a friend of theirs named Odrin. Speak with the three soldiers, but don’t expect to get any valuable intelligence out of them. They won’t be able to do anything for you except initiate the quest in the first place. You will have to head all the way to the edge of the area to find the drunkard. He will be lying near a cave entrance to the southwest. You will have to head through the gap in the houses in the lower left side of the level in order to find it. Speak with him. He will drunkenly ramble on about a square fish. You may remember hearing something about this before. This is because the square fish coins are used by the rebels to communicate with one another. Drunk as he is, this man clearly knows something about the rebellion, and thus is of great use to you.
Carry Odrin back to the camp. As you walk in, you will be stopped by a group of guards. You will have several options for dealing with the guards, as they will be suspicious of you and your accomplice. Whatever you do, DO NOT tell the guards that Odrin is a witness. This will cause them to become even more suspicious, and one of the guards will file a report with his superior. This will draw attention to you and your companion, and the quest will fail. Instead, offer to bribe the guard with 30 orens to keep his mouth shut. This is actually the safest option when dealing with the guards. You can also tell the guards that Odrin is your prisoner. This won’t necessarily backfire, but it’s not as clean a way out as simple bribery, either.
Once you get back inside the camp, haul Odrin over to the group of soldiers that you talked with earlier. The drunks will happily accept their fellow soldier back into the fold. Head to the cantina after the reunion. Along the way, Odrin will stumble and you will have to start carrying him again. Once you are in the cantina, it is time for some smooth talking. You will have to find out information about the rebels without being too heavy-handed, obvious, or subtle in your efforts. If you fail to ask the right questions at the right times, you may very well fail the quest outright. It would be a shame to fail after coming all this way, so follow the guide below to get the right questions and answers.
Do not openly reveal your intentions to them, or they will clam up. Instead, say that everybody has become afraid of Henselt, and tell them that they should send a hunter out for him. They will become suspicious, but not enough to make you fail the quest. Now say that you would just like to know who you are drinking with. This will set the soldiers at ease, and they will hand you a coin along with a password. You will now have completed the quest. Return to Dethmold to continue with the story.