Another day another chopper crash, this time the survivors find them selfs trapped at an abandoned research facility. And the only way out... is down to the core. Survivors must escape from half life's black mesa complex.

Another day another chopper crash, this time the survivors find them selfs trapped at an abandoned research facility. And the only way out is down to the core. Survivors must escape from half life's black mesa complex. This campaign uses five maps on each run, the finale is selected at random but can be selected by the player. map names: l4d2_pdmesa01_surface l4d2_pdmesa02_shafted l4d2_pd...