Reward: 400 Renown, 5500 Gold.
After taking this quest from the Guild go to Rose Cottage and talk to the granny living there. It occurs her grandson has been lost in Hobbe Cave and someone has to find him. Guess who's it gonna be.
When you enter the cave, enter the first door on the right. You will meet a bandit, who offers you help searching the place and dividing the loot you both find. Do what you will, but if you want to be evil, he will come in handy in a few moments.
At the end of the cave system you'll find yourself in a big room with a rocky sphere in the middle. A blue Faerie will appear and tell you it needs a human to complete the ritual and you can sacrifice someone else, swapping him for the boy. You can give him the newly met bandit or kill (or do both, in that order). Take the boy outside, watching that he doesn't take too much damage. Go to Rose Cottage with him. It seems the granny wasn't so innocent after all, but this isn't your business any more. Quest complete.