You take the role of Nick Farrel, a technical engineer in Delta Base - the complex that competes with Black Mesa in various research fields including exploration of the borderworld Xen and weapon development. Due to accidental entanglement of two different experiments conducted at the same time the infamous resonance cascade affects the Delta Base as well, bringing the hostile alien lifeforms which infest the facility very soon.
Love the mood.
I really like "Night Xen"
This reminds me of that night mission in Halo where you had to sneak through a desert to get to the ship, very nice.
Love that mission very much too.