In the 28th century, Valerian and Laureline are special operatives charged with keeping order throughout the human territories. On assignment from the Minister of Defense, the two undertake a mission to Alpha, an ever-expanding metropolis where species from across the universe have converged over centuries to share knowledge, intelligence, and cultures. At the center of Alpha is a mysterious dark force which threatens the peaceful existence of the City of a Thousand Planets, and Valerian and Laureline must race to identify the menace and safeguard not just Alpha, but the future of the universe.

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.