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 (Taylor Kitsch) is a navel weapons officer assigned to the ship 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 takng on the invaders, Hopper must also try to live up to the potential his brother Stone (Alexander Skarsgård) and his fiancée's father, Admiral Shane (Liam Neeson), expect of him.