One of a handful of decent expansion packs, this takes the original plot of 'Half-Life' and looks at it from the perspective of one of the 'grunts' sent to 'pacify' the disaster site at Black Mesa. That said, your original  mission becomes quickly subverted due to unforseen intervention, and you  find yourself rushing through a 'Half-Life' parallel universe, sometime  intersecting with the original game. It's essentially more of the same, but  shorter (a terrible shame), although you get an expanded arsenal, and some  useful allies. There's more of an emphasis on multi-character soldier vs  soldier battles than before, and at times this could easily have been  'Kelly's Heroes : The Game', such was the war film atmosphere. Whilst  'Half-Life' finished with a dissapointing trek through an alien world, 'OF'  sticks closely to reality (although you can beam yourself into 'Zen' if you  so desire). The tragic, tragic shame of it all is that you'll probably  finish it in a couple of days, as it isn't very big. Roll on 'Half-Life 2'.