After talking to the Baron, you will play as Ciri in a flashback of how she met the Bloody Baron.
Follow the river bed until you encounter three wolves threatening a little girl on a tree branch. Be sure to collect alchemy ingredients throughout this quest, as they will come in handy and save you time later. After talking to the girl, start following her as she leads the way home. Eventually you run across more wolves, which you will have to kill before moving forward.
Continue along the path and you will encounter a boat with a dead body inside. When inspecting the body be sure to inspect the chest, legs, and belly to make the quest easier later on. After finishing your inspection, you will have to gather some needed ingredients to create a sword oil if you haven’t already. These ingredients can be found along the river bed and from looting defeated wolves.
The ingredients needed are:
1 Dog Tallow
1 Wolf Liver
2 Fools Parsley Leaves
Once you have all of your ingredients, a cutscene will occur where Ciri prepares a fire and creates the oil. Afterwards, follow Gretka to the lair of the Wolf King.
It should be a relatively easy fight if you made the correct oil from earlier, as it will restrict the werewolf’s full moon ability. During the fight I suggest using Ciri’s dodge regularly and only attacking when you have a clear opening. Once you defeat him, there will be a cutscene and the flashback ends.