shadowrulah

I like Serana, she's knifty and what not but it doesn't change the fact that the only reason she wouldn't be captured or killed is because the dragonborn is lawful stupid.

She could hypothetically escape, but at the absolute worst she's now in Castle Volkihar just like she would have been if you helped her. Your rationalizations aren't changing the fact that with the information you have there's no reason to help her and every reason to stop her. When Serana shows up at fort Dawnguard she's standing in a torture chamber that's seen recent use. If you have any doubts about the purpose of that room look at the items called "Torture Tool" and "Torture Tools." Getting false information or no information is always a possibility but it doesn't change the fact it's better from a strategic standpoint than helping her achieve her goals. What if she had walked into Volkihar Castle and fulfilled the prophecy right there. Sure you didn't know about the prophecy but you knew vampires were looking for her and that she wanted to be taken to vampires, that's reason enough to shut it down.

Then kill her or leave her description with every inkeeper and guard in Skyrim or do anything except help her. What would the vampire hunters do about the ancient and difficult to find Daedra blessed vampires? The dawnguard as it stands at that point isn't much smaller than the dawnguard strike force that sacks castle Volkihar, in a stand up fight they could take Serana. If she's disinclined to talk take those torture implements for a spin, maybe that's not your dragon borns style but it's something mine would do and it's apparently something Isran was ready to do to.

Of course it depends on the character you're playing. A dyed-in-the-wool vampire slayer would have course kill Serana on sight, but then, an ax-crazy psychopath might just murder Delphine for fun, which the Main Quest doesn't let you do. On sane, non-pathologically-vampire-hating characters, there's no real reason to kill Delphine, nor Serana when she's entirely non-threatening towards you. Also, if you kill Serana, you don't learn what the vampires are planning. He's not cool with it at all, but at the beginning reluctantly accepts Serana's help (and assumes that, since she was always a vampire from his perspective, she won't want a cure) and by the end grudgingly admits that Serana is an exception to the "vampires are evil" rule. Serana is a vampire being sought out by the vampires you're investigating and in posession of an elder scroll. She tells you nothing about herself other than she wants you to take her somewhere. She exudes suspiciousness. Even if she wasn't a vampire and didn't acknowledge she had an elder scroll just implicitly trusting people like that is ridiculous. Even if you aren't as kill happy as I am the intelligent move is to take her to Isran, and if she complains that she doesn't feel comfortable when you get there inform her it's not really optional. After you've gathered some information and discovered her blood is the secret to destroying the world killing her is easier and more effective than going through the entire plot. His objections last a brief conversation, even if she's absolutely necessary to the plot he doesn't order her put under guard or locked up he just sort of gruffly pays lip service to "I hate vampires" before. He also doesn't point out that killing her is the best possible course of action even if it's just for your paragon hero to say "no it shall not be."

Also, Isran apparently trusts Serana more than you. He knows Falion can cure vampirism and if you become a vampire he refuses to speak to you until you have it cured. He doesn't even mention this as an option for Serana and is totally cool just having her vampire all around his fortress.

I enjoy dawnguard, I like the idea behind it and the features it adds but the story is overwehelmingly awful. It's a barely coherent mess, I totally get that sometimes the story is just a vehicle for cool things to happen but that's not an excuse for just terrible writing. The absolute most irritating one in my opinion is the fact you don't just kill Serana on the Dawnguard side. Any sort of casual listening in Dimhollow Crypt reveals vampires are looking for something but can't quite get to it. You of course release the thing ,because heroes always do that, and discover it's a vampire with one of the most powerful artifacts in all creation, an elder scroll. Your immediate and only possible response is to take her home and just generally do the vampire's job for them. Forgiving that you eventually realize the sacrifice of a daughter of cold harbor is necessary for the Tyranny of the Sun, killing her ruins harkons plan without any fuss Do you have any plot holes that really irk you?