The first in a trilogy of episodic games, Episode One reveals the aftermath of Half-Life 2 and launches a journey beyond City 17. Episode One does not require Half-Life 2 to play and also includes a first look at Episode Two, which will ship by year's end.Sweeeeeeet.
So when does Half-Life 3 come out?
Oh, just in case you don't know what a headcrab is, here's one:
This is what happens when one attaches itself to you: