Fallout 3 Blood Tiest Quest Walkthrough
Look for Lucy West in or around Moriarty's Saloon in Megaton. Talk to her about her family to receive a quest to deliver a message. Finding Arefu is not that difficult. Follow your compass marker with this quest selected and you'll head toward the highway overpass. Climb to the top to be encountered by an NPC named Evan King. Talk to him and he will give you a quest to check on the village.
The first house you need to check is the Ewer house, just to the northwest. Go inside by knocking and saying you're there to check on them. The male Ewer will be very rude to you, but get the checking done and exit the house. Head to the north and to the front door of the next house you see on the left. Knock once again, then go inside and tell the woman that Evan King sent you to check on her. Leave once done. The next house, on the right is King's house, and you can't get inside. Go into the next house, which belongs to the Wests. You will find the bodies of the wests inside. Search them to find nothing, but complete the contact quest. Return to Evan King.
Tell him that you're done checking, and that the Wests are dead. He'll give you an extension to the quest to locate the Family. This ties in perfectly to delivering Lucy's message. Go back down the broken bridge and cross the river from ground level then head toward the map point for Northwest Seneca Station. As you approach, you'll see a small town with subway stairs in the middle. Go down them to reach the Station.
You will have to fight your way through some mirelurks later so be prepared. Follow the path to meet a ghoul named Murphy. He will make a deal with you that he can make ultrajet, but he will require sugar bombs to make it. This is the primary purpose for Sugar Bombs in the game. Go through his little outpost and down the hatch. Make your way through the tunnels, through the mirelurks, into the subway. Once you reach the subway the path is linear, so don't worry. You will likely meet a dead end then have to double back and take the path that is to the right (if you are now facing the opposite direction). You'll find the Wests' gatekeeper.
Tell the gatekeeper that you have a letter for Ian West. Once inside, take the southbound route when you get to the subway door. You will eventually come to the Family, whereupon you should speak to Vance. Talk to him kindly and ask him about his family and Ian. He'll have you learn their laws. Talk to all of the Wests and ask them about the laws, and you'll learn five messages that lead to vampirism.
Talk to Vance again, and be nice. If you lead to the end of a conversation, speak to him again and talk about Ian. You'll eventually be given the code into Ian's chambers, which are up the escalator and to the left. Activate the computer terminal and disengate the door locks. Talk to Ian and tell him you have a letter from Lucy. He'll decide he should go back to Arefu. You should now head back and talk to Vance. If you can tell him a deal that involves the speech, medicine or intelligence skills, take it (med and int are guarantees). You will learn the Hematophage perk, which allows blood packs to heal 20 hp instead of a single hit point. Return to Arefu and talk to Evan King to finish the quest.