This task is automatically added to the journal after completing the Nilfgaardian Connection main quest. More specifically, after examining the chest in the basement in Heatherton (M3,2). Main objective of this quest is meeting with the baron. To do so, you must reach his castle, which is located south from the Crow's Perch village. After arriving one of two situations will occur. It depends on how you reacted to baron's men in the Inn by the Crossroads.
Reaching baron - option A
If you were not aggressive towards the people at the inn and used friendly options during the timed conversation, then the guards standing on the bridge leading to the castle won't react to Geralt's arrival. Use the bridge at the moat and then reach the closed gate leading inside the building. After a short conversation with baron's men, you will receive permission to meet with the baron. Follow the sergeant to the place where the baron resides.
Reaching baron - option B
If you have murdered the bandits in the inn, then the guards will run away the moment they see you. Enter the building and be ready to fight a group of baron's henchmen. Be especially cautious of the enemy with a shield. Try to stun him and then attack him from the flank. After the battle, head towards the closed gate leading to the main courtyard of the castle. You will learn that you can't enter without permission. Remain in the perch and search for a peasant. Talk with him. Give him 15 crowns and you will learn about an alternative way of getting to the baron.
Leave the perch and get to the marked shrine the the north-west. Get close to the water and you will uncover an underwater tunnel. Dive in there and you will reach a large cave. While exploring it, help yourself with Cat potion or a torch. You must be careful - there are water hags living in the cave. To eliminate them, use the silver sword, Igni sign and Northern Wind bombs (if you have them). Find a lower ledge in the cave, climb on it and reach the well. Use the ladder and you will get to the location where baron resides.
Both situations described above will allow you to meet with the baron Philip Strenger. During the conversation new quest will activate: Ciri's Story: The King of the Wolves. After completing Ciri's quest (100 experience points) and regaining control of Geralt, you will obtain new main quest Family Matters and an optional quest Ciri's Room.