The Payback event first of all requires you to do the Hunt for Werewolves quest of him.
Then, there is a randon chance when you enter the Sawmill, you'll tale a pick at Logan mad and unable to control his transformations.
The third step is visiting Bareshade at night, you'll find Logan at the entrance and he'll just go and let you there.
If you want to start the event, right after talking to him, open the map and go to the forest, to the Den, and find him inside the door at the end of the map.