Received from: Zyvik (M25, 6). Appears there only until your first visit.
Step 1: Find the soldiers
Once you leave the camp for the first time, you will come across Zyvik, who will tell you that two soldiers had gone missing - you're to send them back to the camp when only you meet them. The soldiers can be found at Sabrina's execution site (M23, 5) and after a short talk they will tell you that they didn't have the courage to come back, because of the monsters. Before heading back, you have to investigate the site and then decide whether to give them the nail or not.
Notice! You have to agree to take the soldiers back, or else they won't want to talk with you anymore.
Step 2: Escort the soldiers to safety. Defend them from monsters
Head towards the safe place (M23, 6). On your way however, you will get attacked by a group of Drowners. Try to defend the soldiers at all cost, remembering about Quen and Aard to push the monsters away from your allies. After reaching safety, the guards will return to the camp on their own.
Step 3: Get your reward from Zyvik
Return to the camp as well and find Zyvik (he'll be walking through the camp - more or less following the same path along which he gave you a tour), who will reward you in return for finding and escorting the soldiers.
Prize: 100 XP