Disaster! An alien invasion and subsequent infestation have decimated this facility. Many lives were lost, the facility was ruined and the aliens were unstoppable. All hope was lost until one survivor found the courage to fight back and put the aliens in their place! It was a long and horrific battle as the survivor dueled with all manner of horrific life-forms and alien mutations, but our hero won out in the end and destroyed the alien menace! Humanity was saved!
Unfortunately, the alien infestation and the heroic efforts of the courageous survivors have left rather a mess thoughout the facility. As the janitor, it is your duty to get this place cleaned up. So grab your mop and roll up your sleeves, this is gonna be one messy job. Today you're on Viscera Cleanup Detail!
Source: The Developer Website.