You are a normal marine, no more important than the rest. You've worked at the UAC for years now, and have had time to learn about what all of their funds go to. They research inter-dimensional travel and genetic alterations. However, the UAC, as you have recently learned, is corrupt. They let it be known that experiments are only done on willing individuals, but that isn't true: one of your fellows was reported as "mysteriously missing" and never found again. One night, at your workstation, you decide that these corrupt bastards are going down. It's going to be a tough fight, but you have to kill a few to save many.