Kill the Voidwoken inside the house.
You met an elderly couple, Lyn and Conway Pryce, trapped in their farmhouse by Voidwoken.
Kill the voidwoken, then ask for your reward.
This quest can only be started if you complete Burying the Past by killing Jonathan before crossing the Paladin bridgehead, otherwise Burying the Past will be auto-completed (and assume that Gareth spared Jonathan), which results in the death of the quest-givers.
Tips & Tricks
Lyn and Conway are Gareth's parents and will be dead if the player does not kill Jonathan in Burying the Past.
Almost all Voidwoken are ranged and attack magic armor (Tactician difficulty).