When mankind beams a radio signal into space, a reply comes from ‘Planet G’, in the form of several alien crafts that splash down in the waters off Hawaii. Lieutenant Alex Hopper is a weapons officer assigned to the USS John Paul Jones, part of an international naval coalition which becomes the world's last hope for survival as they engage the hostile alien force of unimaginable strength. While taking on the invaders, Hopper must also try to live up to the potential that his brother, and his fiancée's father—an Admiral—expect of him.

After escaping with Newt and Hicks from the alien planet, Ripley crash lands on Fiorina 161, a prison planet and host to a correctional facility. Unfortunately, although Newt and Hicks do not survive the crash, a more unwelcome visitor does. The prison does not allow weapons of any kind, and with aid being a long time away, the prisoners must simply survive in any way they can.