The year is 1941, the height of the second world war. Unbeknownst to the world, Germany has been slowly investing in biological weapons just like the United Kingdom. The cause of it all was the discovery of a meteorite that contains an extraterrestrial substance, außerirdischem. Außerirdischem seems to have the potential to be developed into a virus that can achieve mass destruction. Hence the Germans brought it back to their top-secret facility X13 for further research to develop it into a powerful biological weapon. But unbeknownst to the Germans, außerirdischem is in fact a sentient parasite, capable of infecting and taking complete control of its host.
You are außerirdischem, also known as außerir for short. As a parasite, you can only infect a single human carrier at any point in time. Take control of scientists one at a time, outsmart bodyguards and escape the depths of Facility X13!