Stopped reading after "After experimenting one the player for years".
And because that was a lie, "The main continues" also annoyed me. Also, do you even know what a vaccine is?
Now that I've satisfied my inner editor... The story is alright. But that's about all I'd give it. Maybe it was just the way you wrote it which didn't convey what you meant properly, but the first paragraph seemed very loosely connected, and I can't really see how it'd work well ingame. The rest of the story isn't too bad, if not a little cliché.
On that note, the inclusion of what I presume is the g-man (knowing you) is
A- Not really going to be appreciated by anyone other than HL players (yes, I realise that's the only people who'll play it, not the point)
B- Not entirely beneficial to the story. It doesn't make a whole load of sense.
C- The purpose you've given him (explanation of the character's background) could be done in better ways, like overhearing a conversation.
But I'm just negative. If you put enough effort in, I'm sure you're capable of making this mod well.
P.S. It's been said a billion times before, yet no-one seems to listen. If you want to attract a team to a project, display some media first! No-one is going to join a project solely on a storyline.