Kill the Pigsbane and report to Syrus Oates. 

Cast Spirit Vision in the sawmill, you will find a mute spirit, and learned that his name was Syrus Oates. He was burned alive by Pigsbane, a Lone Wolf, but did not scream despite the agony. He now wants Pigsbane dead.

After you killed the Pigsbane, return to Syrus Oates for reward.