In this task you must find the hiding place of the deserters. You will learn about this quest by reaching a small camp in the northern part of the map (M1,8). In the camp you must examine a corpse and the chest, and take Spy's Notes. Read it in the inventory.
Set this quest as active and go to the Mill on the West. Take an interest in a hut near the mill (M1,9). Walk inside. You must unlock the passage down, it is easier to do it with Aard sign. In the basement you will find few containers. To complete the quest, you must loot the ones with Vrihedd Brigade Sword and Hunting Trousers.