Fallout 3/Main Quest Walkthrough
.. Beginning coming later ...
Picking up the Trail
You are dropped of at the entrance of the Citadel. Talk to Elder Lyons to get some more background. Now go to the scribe to get more details. Just follow the arrows from the game. The scribe is in a large room that has two levels, you will enter on the upper level and the scribe is in a corner on the lower level. Find him and talk to him.
He tells you to go look at a prewar computer about Vault Tec equipment. Follow the Arrow to the A-Ring area and there to the archive. The arrow indicates a single terminal, just go there and use it. Go for the first entry (DC Area Vault Listing) and then select Vault 87. Now select Equipment Issuance and go to the second page. Here you will find that this facility has one of the G.E.C.K. units you are looking for.
Return to the scribe where you were before and talk to him. He will show you on a map where Vault 87 is, but there is a slight problem, the entrance is highly radiated. So your only chance is the backdoor through Lamplight Cavern, some tourist attraction. Gear up and head out to there.
You might want to finish up any business you had now, as the next few parts are pretty much the end of the game. Once you enter the cavern, you are pretty much set on a chain of events to complete the game and there is no "open end" in Fallout 3, once it's done, it's done.
Travel to the Lamplight Cavern and enter.
.. Part in progress ...
The American Dream
After you have been captured in Vault 87 you are taken to Raven Rock, the hideout of the Enclave and President Eden.
Do not tell the Colonel Autumn anything (don't lie either, like giving him the wrong code). He will get fed up and then the president calls him away. Now the president has a little talk with you and invites you to talk to him.
With the restraints gone, grab your stuff from the locker. Remember to wear your armor and weapons again. Leave the cell and a guard stops you. Either sweet talk the guard (if you have the skill) or simply state you are supposed to be there. The guard will check with the president and you can move unhindered. If it goes sour, that guard and two soldiers will attack you. Kill them and the President will announce to let you pass.
Easiest is to follow the corridor to the right from your cell. Go around the concourse to the door for the labs. Enter it, then in the middle to your left are stairs up, go up, turn left and take the door in the next room to Level 2.
The colonel doesn't like you. From here on out everyone is hostile. Fight your way to the northwest area, there are quarters there and the corridor goes in a long stretch south to north. IN one of them on the west side you will find an old acquaintance of your fathers. Just ignore her and go further north through the different looking door.
Now here there are two doors. The on to your right at the end of the corridor will open and two soldiers come out. Take them down, then go into the room on the left first, before going through the door the soldiers came in.
This room has two hidden gems for you. One is the Bobblehead for energy weapons on the table, that gives you extra energy weapon skill. The second is in a foot locker, just across from the table where the Bobblehead was. You have to pick or force the lock on this one. Inside is the ZAX destruction sequence. Go to notes on your pipboy and listen to it. Seems like there is a backdoor to kill the president.
Go through the door across the hall and follow it to the round war room, then go to the left into a new section of the area.
Here two bots and two soldiers wait. Just take cover and let the bots kill the soldiers. With them dead, proceed to the control room. Take the stairs all the way to the top and meet the president.
He want's you to put a virus in the water supply. You will have to take the vial to continue. If you have the ZAX code, you can have the president self destruct or if your speech skill is high enough convince him to kill himself. It does not have an effect on the later course of action though.
With that leave through the door just behind you. It's all straight forward. The bots will assist you in killing the enemy guards, so let them do their stuff while shooting at the enemy from behind cover. You will get to the exit of Raven Rock and back into the waste land.
Outside you will meet Fawkes the super mutant again from Vault 87 (if you decided to help him). If your karma is good, you can have him as your companion, otherwise he will walk off on his own (to the Museum of History).
Return to the Citadel.
Take it Back!
Inside you witness a conversation then you get pulled into it. If you talk about the virus to the elder, you an give it to him (or simply not use it later). The pride makes you a honorary member. Now you can buy their armor and weapons from the armory (just behind the place they are standing). Gear up and they release the big robot.
Go outside and now comes the easiest part, stay alive. Just follow the big robot around, at a good distance behind. Kill the occasional straggler enemy that the robot misses (which aren't many, it's very effective) until you reach the project. Enter through the door for the gift shop.
Inside kill the guards and do yourself a favor and save before you enter the roundabout where the project is housed.
Now you meet the Colonel with two Soldiers. Kill all three and you are almost done.
Step up to the control room. Now you have multiple choices that only effect the end dialog. If you want to, you can save here and try them out. You can or cannot enter the virus (the box in the airlock straight ahead when you enter) and once the intercom conversation is done, you can either go in yourself or let Lyon go in. Either way, the code is 216 (your characters mother favorite quote) and with either you entering the code or her stepping into the chamber, the game comes to it's conclusion.