The Enemy Within...
Hettar Fjordson is a young warrior in the Horse Clan who has been rising through the ranks rapidly. The favored nephew of Horse-Lord Alric Rangvaldson, he started his military career just a few short months ago, and soon distinguished himself in local scouting and patrol duties, earning a number of kills in small border skirmishes. Showing leadership potential, as was expected, Hettar was given his first command. The young horseman set out with his scouting party into the borderlands and never came back.
Ever since his disappearance, Urgals from the nearby Ironfang tribe have been making raids into Horse Clan territory. They grow bolder with each new attack, and their tactics show a startling level of intelligence and strategic planning. Their new abilities suggest an insight into the ways of the horse people, and rumors are spreading that Hettar has been captured and is being forced to aid the Urgals.
A man approaches the PCs on behalf of the Horse-Lord himself, hoping to hire them to head into Ironfang territory and discover the source of the Urgals' newfound strategies. If Hettar is indeed held captive, they are to rescue him.
When the PCs arrive in the Ironfang warcamp, they discover that Hettar isn't being held captive by the Urgals....he is leading them! Something has convinced the young warrior to work with the Ironfangs against his people, and it is up to the PCs to convince him the error of his ways, or else kill him to prevent further attack.
Also, I like the variant fighter, sounds like a good plan, especially for this world.