After the Black Mesa incident... Save your own skin from the military and creatures warping in from Xen.
After having beaten HLE years ago, I was astounded to learn there was a sequal.
Both mods capture the essence of Black Mesa perfectly and offer plenty of thrills throughout each campaign and great level design, with the second spicing up the combat with higher-def models and custom features that bring the firefights to life.
The ending was a bit of a downer, but unexpected and of epic proportions (On Gold Source, anyway)
So if your crazy for more Black Mesa content then hold on, because the Escape series will give you a ride you won't soon forget :D