With the first wave, they took out a third of the human population. With the second wave, they make us take out the rest.
In the first wave, the invaders came with the snow. The rose up with their icicle teeth of death and destroyed over a third of us on planet Earth. But they weren't finished by a long shot. The survivors have fought for their own lives. But the invasion wasn't over with the first wave and the survivors aren't as safe as they thought.