- Talk to Lord Gemma at his estate (twice)
This quest starts automatically once you pick up the Bill Lord Harikari dropped when he died.
Go back to the road you left to kill Lord Harikari. Follow it Northeast to Blessed Rock Manor (you might want to fight off any enemies following you at the gate, where the Guard will help you). Head directly North from the Manor gate up to the house itself. The entrance is on the right (East) side. Head inside and to the back of the ground floor, where Lord Gemma is standing near a desk.
Talk to him and he will deny he owes you money.
I don't owe you any money. Get lost!
Talk to him again and he will change his mind and give you the money, completing the quest.
I guess I made a mistake, I do owe you money. Here take it!
- Note: Although you have to complete the Lethal Escort quest to get the Bill that triggers this quest, the two are not considered to be a chain by the game.