In the 28th century, the remnants of the International Space Station have evolved into "Alpha," a vibrant metropolis where countless beings from various planets coexist harmoniously, sharing their cultures and knowledge. To maintain order and peace across the universe, the humans have established a unique police division composed of officers like Valerian, a carefree major, and his pragmatic partner, Laureline.
During a mission, Valerian experiences a vivid dream of a tranquil planet inhabited by a primitive humanoid race that harvests pearls rich in energy and utilizes small creatures to duplicate them. Suddenly, disaster strikes as debris cascades from the sky, culminating in a catastrophic event when a massive ship crashes, obliterating the planet's surface. Amid the chaos, a female humanoid, a princess among her people, becomes separated from her group but sends out a desperate telepathic signal before the explosion engulfs her.
Startled from his dream, Valerian learns his current task involves retrieving a rare "Mül converter," known for its ability to replicate anything it consumes, even currency. This crucial item is the last of its kind in existence and is in the possession of a black market dealer. As he prepares for the mission, Valerian proposes to Laureline, but she dismisses his offer, well aware of his flirtations with their female colleagues and his tendency to treat serious matters lightly.
Upon arrival at the bustling "Big Market," Valerian unintentionally interrupts a meeting between the dealer and mysterious hooded figures. There, he discovers that the elusive "converter" is one of the creatures from his dream. Together with Laureline, they secure the converter, and Valerian discreetly pilfers a pearl meant for the dealer, intending it as a surprise wedding gift for Laureline.
Upon their return to Alpha, their stern superior, Commander Filitt, reveals that an unidentified toxin has infected the station's core, making it highly dangerous. Their mission is to safeguard the commander during an upcoming inter-station summit aimed at addressing this crisis. While Filitt requests the converter, Valerian insists that Laureline should retain it until their protection assignment concludes.
The summit takes an unexpected turn when the humanoids launch a sudden attack, incapacitating the attendees and seizing Filitt. Valerian, breaking free from his restraints, pursues the kidnappers into the toxic region. However, he loses control of his vehicle, and Laureline is left unable to communicate with him.
Disregarding orders, Laureline finds an unconscious Valerian at the edge of the infected area but is then taken captive by a primitive tribe. Valerian infiltrates their territory with assistance from a shape-shifting dancer named Bubble. After rescuing Laureline, they narrowly escape, though Bubble sustains fatal injuries and urges Valerian to continue his pursuit of Laureline before succumbing.
As Valerian and Laureline delve deeper into the contaminated zone, they discover it is not radioactive at all. They eventually stumble upon a vast, protected hall harboring the captive Filitt and the humanoids. Their leader recounts the tragic history of his people, who were peaceful inhabitants of the planet Mül until a battle erupted in orbit involving the human fleet. Under Filitt's orders, a devastating weapon annihilated both the enemy and the population of Mül, a fate Valerian had witnessed in his dream, sent by the princess and daughter of the humanoids' leader. A handful of survivors managed to escape in a downed spaceship, where they absorbed knowledge of technology and history, ultimately seeking refuge in Alpha. They constructed a spaceship designed to replicate their lost paradise, and the hall they inhabit is the very vessel they have crafted.
Filitt, admitting his complicity in the genocide, contends that the doomsday strike was a necessary evil to end the conflict, and that the subsequent cover-up was essential to preserve human interests in Alpha. As the spaceship prepares for launch, Valerian offers up the pearl he acquired, while Laureline possesses the converter. Initially reluctant to part with the converter due to its status as government property, Valerian ultimately yields to Laureline's plea, recognizing the injustice of their government's actions.
In a dramatic showdown, Filitt's robotic soldiers, pre-programmed to attack the humanoids, confront Valerian and the government troops. With Valerian's brave efforts and the support staff's assistance, they manage to overcome the hostile forces. The spaceship takes off with Valerian and Laureline aboard, while Filitt is taken into custody. In a tender moment aboard their own vessel, Valerian and Laureline profess their love to one another, dreaming of reaching their paradise within a mere two hours.
