After cleaning out the Deathclaw Sanctuary - and finding a magical bobblehead that increased my endurance by one, I decided that I'd explored enough, gained enough levels and that it was time to get back to the serious business of finding my dad and helping him out with this whole saving-the-world thing.
I return to the Jefferson Memorial and find that the interior is as cram-full of Super Mutants as the exterior was. Thankfully, they're almost no challenge at all at this point, unless I let the ones with a sledgehammer get close.
I find dad's lab and some tapes. It seems that he found evidence of something called a G.E.C.K. - basically a Do It Yourself Terraforming Kit - and that he went rushing off to Vault 112 - the place where he believes the Doctor Braun guy who built this thing eventually settled.
The Vault is fairly close to Fort Barrister. I fast-travel there only to wind up in the middle of a fire-fight between the two renegade members of the Brotherhood of Steel and a bunch of Talon Mercenaries with dogs and robots. I guess they're taking me a bit more seriously now that I'm level 17.
The journey to the Vault, hidden inside an abandoned garage, is uneventful. Shoot roaches. Shoot mole rats. And then I find... friendly robots who offer me a change of clothes and ask me to sit down in the life pod. Next thing I know I'm in Mayberry. Or Pleasantville. Well, a reasonable facsimile anyway. I'm trapped in a kid's body and everyone tells me to go play with Betty, a girl in the playground in the center of town.
Betty is mean and tells me to go make one of the neighbor boys cry. Deciding that there's obviously something screwy about this place, I opt instead to just wander around, after having a nice talk with Doc The Dog.
Eventually, an old woman comes out, insisting that the world around us isn't real and that they're all trapped in a computer simulation of reality. Uh... yeah. I've seen The Matrix. But in this case it's all the fault of Dr. Braun - the jackass my dad was looking for who is apparently still alive, kept in cryogenic suspension by the life-pods... a virtual god in this world of his own design but bored and wanting amusement. She tells me that there's an abandoned house nobody is meant to go into.
I go there, find a bunch of random objects and find that messing with the objects creates tones. Eventually I work out the "code" and make a computer appear in the wall that lets me "hack the Matrix". And by Hack the Matrix, I mean unleash an army of Chinese soldiers who gun down everyone except me, Betty and Doc the Dog. Somehow, this gives me good karma, even though these people dying in the game kills them in real life.
(Side Note: I looked at the guide on-line later and found out that had I gone on to make the boy cry, I could have begun a reign of terror that would have also eventually lead in the entire town being killed and netted myself a ton of bad karma. I guess the logic is that by having them gunned down quickly, I am putting these people out of an eternity of torment quickly rather than by making them suffer as I would have by following Betty's instructions.)
Anyway, it turns out that Betty is Dr. Braun, that he did indeed get bored of the virtual paradise he had created.... a tropical island then a ski chalet... and decided to make something like his childhood neighborhood... and he had gotten bored again. However, by doing what I've done, I've trapped him in this reality alone forever, since the game won't allow him to die. Seems that essential personnel have a god mode that can't be shut off. Sucks to be him.
I get out of the pod and find Dad (he was Doc the dog), who thanks me for rescuing him. We have a heart to heart about things and I agree to help him with getting Project Purity - the project to clean all the radioactive water in the wasteland - up and running. We head back to Rivet City, gather up the scientists there and head back to the Jefferson Memorial.
I'll spare you the fine details. Suffice it to say I clear the basement of Super Mutants and then run around the place activating equipment in order to get the water pumps activated again. By the time I get back to the control room, there's a bunch of guys in Power Armor there, hassling my dad and insisting that he activate the facility, which is now under their control.
Well, Dad winds up blowing the reactor, killing them all and himself... and having just enough time to collapse against the glass, look up at me and say "Run"....
And that's where I had to stop because - due to a game bug - I couldn't follow the fleeing scientists through the secret passage they used to evacuate the complex. So next time... fleeing the Memorial. Maybe.