Napp was a peasant who lived in White Orchard. One night in 1272, he got extremely drunk and proceeded to set fire to the local blacksmith's workshop, believing the dwarf, Willis, had been profiting off of helping the Nilfgaardians not to mention Napp's general dislike for non-humans. However, on the way home, he ran into drowners and while he managed to escape them, he suffered a bad injury to his right hand.
If Geralt turns him in: Napp was sentenced to death by hanging as the Nilfgaardians viewed his act as a crime against their war efforts.
If Geralt accepts his bribe: Napp wasn't turned in and the witcher simply told Willis he couldn't find the arsonist.