The Problem:
I just got a side quest called "Rescue Mission" from the Companions to save him. I get to the location for the rescue mission (an underground cavern in the middle of a lake infested with vampires, I forgot the name at the moment) and I kill all the baddies, but he's already dead in a cage. He has an arrow over his head. The quest logs says "Talk to [NPC name here]". I can't. He's dead.

I can't get another Companions side quest until I finish this one. But I can't finish this one because the NPC is dead. The "resurrect" console command doesn't work on him. There's no failure message, he just doesn't res.

Is there any way to abandon the bugged quest?

Who the NPC is and where he died:

I found a list of console commands a person had used, one of them was to fix this very problem. I've not used it myself so I cannot guarantee it will work. The command itself should not be abused in a game as it can cause problems with bloat I believe.

place.playeratme NPC-BaseID Theoretically it should place a living npc and you might be able to proceed with your quest. You'd have to find the base id of this npc. Of course you'll save before attempting this so I don't need to say to do that.

You can also use setstage to complete the quest. Find the ID of the quest and the stage of finished safe deliverance in home town.

The SetStage console command did the trick. I used ShowQuestTargets to figure out the quest id and then use SetStage [quest id] 50 to set the quest to failed. SetStage 10, 20, 30, 40 didn't seem to do anything. SetStage 100 seemed to advance the line too far. I couldn't find anywhere online to figure out exactly what stage was correct so I just tried a few.

Anyway, just thought I'd post the solution in case anyone else needed to fix a similar problem.