In the sidequest "Childplay" you help the child Mike finding his friend Mill.

Mill was put in his room with the door locked by his father Griblook. If you stand at the door you can talk to Mill through the door. Mill tells you that his father got angry for something he did and locked him in and threw the key down a nearby well. You must go to the well and pick up the key, it lies just next to the Slumbering Dragon inn, where Griffith is standing.

After you do that you go back to Mill and to sneak past Griblook you hide Mill in your cape. You must walk to the door and don't approach Griblook or you get caught.

Simply talk to Mike again and they both will reunite and you get a Defense aura as a reward.