So obviously there's a 150 day time limit for the waterchip mission, perfect no problem. I however just finished slaying every single body in the Mutant Military complex out west and my god to my surprise post seft-destruct sequence a video of Vault 13 being overrun by mutants kicks in??? WTF? do you have to kill the mutant master first? I have no clue, I've only ever played the 2nd one. Bear in mind on the calendar it is nov 2nd at 2 am.... Yup that's right I spent the whole summer runnin around like a cowboy unconcerned about storming the military base until I had sufficient HP, armor and LVL stats, cuz I'm mental and I wanted to slay the whole nest single handedly.

Anyone aware of what might be the cause of this unsettling event?

-B

If you played the unpatched version, there's a hidden 500 day limit to finish the game, otherwise the mutants overrun Vault 13. It's a pretty silly mechanic and was patched out of the game eventually.

That raises the question of why you're playing without patches, though.

Yeah, as far as I know that 500 day limit (lowered to 400 if bought water from Hub) was completely removed in a patch. So if the game is up to date, there shouldn't be an unexpected game over.

Then again that 500 day timeframe is still more than enough to do absolutely everything in the game or at least most of it. Fallout 1 isn't really that long game overall.