It all started when I noticed Vilkas had strangely gone missing from Jorrvaskr recently, I had completed the companions main quest-line and was on to the side-quests. He was the only leader I never saw when trying to "talk to the companion leaders for work". I didn't think much of it at the time and continued to trudge through the game.
So I was ambling along a small secluded mountain path when I came across your typical Pyromancer-Cyromancer battle blocking my path. I then preceded to enthusiastically throw down a few ice-storms and thunderbolts to destroy them. I succeeded, but to my annoyance I found a horse trying to trample me from behind having apparently been accidentally shocked during the battle. I didn't bother to kill the horse and soon it ran off down the path anyway.
A couple of minutes later I came across the same horse again (probably, there wasn't that many horses running around where I was) standing next to a dead Breton woman. I searched her and found she had a "corpse note". Upon reading it I learnt that she was attempting to recover something from the forsworn, and had obviously failed :L. Then (this is where it gets strange) a dead hagraven casually flew out of the ground in-front of my character, scaring the s**t out of me. As the hagraven flopped back down again I spotted a familiar face running towards me.
Of course, it was my old shield-brother Vilkas. I didn't even have the time to say "how's things?" before he brought his great sword down on my pretty helmet. As shocked as I was, I didn't fail to notice he had brought someone called "Mia" with him (any ideas? name seems to ring a bell) and she began to strangely take out her anger on the horse. As I couldn't kill this confusing pair, I was forced to freeze them with Ice form and peg it down the side of the hill.
The next day (real time) I discovered that Vilkas had returned to Jorrvaskr, and was stood in the training area. What's more, when I approached him the cheeky little prat tried to force a job on me! Well, I can safely say I won't be doing any more work for that traitor, and to think I used to call him my shield brother.
