UFO: Aftershock Patch 1.3
The year is 2054. Fifty years ago, something terrible happened and the surface of Earth became uninhabitable.
The Reticulans who invaded the Earth are not true representatives of their kind, they are a breakaway faction that burned the bridges and chose this backwater part of space to conduct its experiments.
The Reticulans would construct a large satellite (several kilometres across) with a closed ecosystem and move the remnants of human population there. The experiment with the Biomass would go on on the surface. Then something went horribly wrong... You now have to save all of them!