Lost Lambs is technically a side quest in The Witcher 2, one that you will obtain when leaving the camp for the first time. However, completing this quest will give you access to extra evidence and information during your hunt for the assassins during the Assassins of Kings quest, so this guide will cover it in the main story section. Zyvik will be just outside of the camp to the right, searching for two of his lost men. He will ask that you find them soon so that they may make the muster on time.
Agree to help Zyvik find his lost men. He will tell you that they vanished in the gullies somewhere. Head back to camp and to the south, towards Sabrina’s pyre. When you reach the pyre, you will find the lost soldiers. Speak with them to learn that they have become stranded, in a way. Scared of the Drowners patrolling the camp, the soldiers have decided to stay put at Sabrina’s pyre until the monsters go away. The drowners cannot enter the enchanted circle around the pyre, meaning that they are safe for now. After completing the Blood Curse quest (which you should have, if you have been following the guide,) come back to them and make a choice. You can tell them that they are good to leave on their own, or you can agree to escort them back to camp. If you tell them to go on their own, they will sadly die and you will not receive the extra bit of information in the quest The Assassins of Kings. This will also lead to the failure of the current quest. Instead, you will want to escort them back.
Draw your Silver Sword and get ready to fight some Drowners. These are relatively weak enemies, and should only take two or three swipes from your Silver Sword to kill. Escort them all the way back to camp to receive 100 experience points. Now, head out to find Zyvik. He will not be in any one location over another, as he tends to wander about the camp, so merely explore the area around the workshop and the borders of the camp until you find him. He will be marked by an in-game waypoint if this is your active quest, making it a bit easier. He will reward you with 110 orens and the Lost Lambs quest will be completed.