My favorite quest line is the early part of the Deshaan quests, where a group called the Maulborn go around peddling a curative purported to treat a disease that turns people into zombies. In fact, the curative is what turns people into zombies. Under the disguise of curing what ails you, the Maulborn medicine causes what ails you. As you ramble through Quarantine Serk (killing these evil pharmacists and their henchmen), you find papers that indicate that the early versions of the curative aren't strong enough and another, more potent batch will be needed to turn Dunmer into Zombie Husks more speedily. Later, you'll encounter the Chief of the Maulborn alchemists and slay him after he threatens to "experiment upon your body." Now, why do I like this quest line? Um. Let's discuss that another time.