We're here to stop the Greys from interfering with human development, which they're doing with their hybridization project. They want to manipulate your genome so that you all evolve into Greys. Since we're the natural future version of your species, if the Greys succeed with their interference, we'll never exist.

Obviously we can't allow that to happen. So our primary mission is to stop the Greys' invasion in 2012. That's when they plan to begin forced integration of their Hybrids into human society.