In the 23rd century, to discover the fate of an expedition sent 20 years earlier, starship C-57D reaches the distant planet Altair IV. Dr. Edward Morbius (Walter Pidgeon), one of the expedition's scientists, contacts the starship. He states no assistance is required, warning the Earth ship away, saying he cannot guarantee their safety. Commander John Adams (Leslie Nielsen) insists on landing.
On an asteroid, the Terran Federation's Fort Casey is crawling with bugs. The starship Alesia begins to deploy its Mobile Infantry troopers, by dropship, to seize and control the hangar and rescue any survivors. Lieutenant Daugherty's 'Alpha' team lands and immediately engages bugs, fighting through to rendezvous with the surviving Fort Casey troopers. After setting explosives charges, the troopers head to the starship John A. Warden for evacuation, only to see it leave dock without them – Minister Carl Jenkins has commandeered the Warden from Captain Carmen Ibanez, sending her to Alesia. Before leaving, Jenkins orders that Major Henry "Hero" Varro, the commander of Fort Casey's K-12 troopers, be escorted to Alesia as a prisoner. Alesia docks with Fort Casey for emergency evacuation of the surviving troopers, and the Fort Casey asteroid is successfully destroyed.
The film begins with an alien ship crash landing on a desert planet. The alien survivors, known as Vecarians, are quickly killed by the planet's predatory native inhabitants, the Selenites. The ship's core, Vecanoi, survives, and from it sprouts Axis, a massive tree reaching up into space.
Meeper, the janitor of an alien pub called the Ale-E-Inn, has higher aspirations—a karaoke performer. After he accidentally electrocutes a singer, he is ejected from the pub. Outside, he is told by an incautious Gungan that "The ChubbChubbs are coming!" Meeper sees aircraft land in the distance, and huge, weapon-bearing monsters exit the craft. He assumes these are the ChubbChubbs.
In 2069, the unmanned Sun Probe locates a planet lying on the same orbital path as Earth on the opposite side of the Sun. Dr Kurt Hassler (Herbert Lom) of the European Space Exploration Council (EUROSEC) has been relaying the spacecraft's flight data to a rival power in the East; after tracing the transmissions to Hassler's laboratory, Security Chief Mark Neuman (George Sewell) catches the scientist in the act and kills him. EUROSEC director Jason Webb (Patrick Wymark) convinces NASA representative David Poulson (Ed Bishop) that the West must be the first to send a mission to investigate the planet. With EUROSEC member states France and Germany unwilling to provide financial support, Webb obtains majority funding from NASA; American astronaut Colonel Glenn Ross (Roy Thinnes) and British astrophysicist Dr John Kane (Ian Hendry), the head of the Sun Probe project, are assigned to the mission.
In the distant future, the gargantuan blue humanoid Draags have brought human beings (who are called Oms as a play on the French word for "man", Homme) from Earth to the planet Ygam, where they maintain a technologically and spiritually advanced society. They consider them animals, and while some Oms are kept as pets by Draags, others live in the strange wilderness and are periodically slaughtered by the Draags who wish to keep their population controlled. Draags have much longer lifespans than Oms, but reproduce much less.
The peaceful planet of Jillucia in the Andromeda galaxy, has been conquered by the steel-skinned warriors of the Gavanas Empire, whom have turned the planet into a military fortress. Kido, leader of the tribes of Jillucia, sends out eight Liabe Seeds to find those who can liberate their planet. Kido's granddaughter, Princess Emeralida, and the warrior Urocco follow the seeds into space.
Sur la planète XT-59, un groupe de six prisonniers se voit condamné à l'exil sur une planète hostile. Devant eux, à perte de vue, des steppes glacées où nul ne peut survivre. Sous leurs pieds, une menace plus grande encore. Leur seul salut : atteindre l’Île, un havre de paix où ils pourront trouver refuge.
The peaceful people of Gandahar are suddenly attacked by an army of automatons known as the Men of Metal, who march through the villages and kidnap their victims by turning them to stone. The resulting statues are collected and then transferred to their base. At the capital city of Jasper, the Council of Women orders Sylvain to investigate. On his journey, he encounters the Deformed, a race of mutant beings who were accidentally created via genetic experimentation by Gandahar’s scientists. Despite their resentment, they are also threatened by the Men of Metal and offer to help Sylvain.
In an asteroid excavation, space crewman Tyler and his colleague find a green crystal that is rumored to be the key to a fountain of immortality, however, it makes whoever touches it insane. Tyler ends up killing his mining partner, and takes over the ship, killing most of the resisting crew except for Dr. Schechter, and the pilots Lambert and Germain. His search for the planet with the fountain leads to Eden, a planet that is designated F.A.K.K.² (Federation-Assigned Ketogenic Killzone to the second level), but has inhabitants whose bodies carry the immortality fluid. Tyler invades Eden, and kills the Edenites, but captures some so he can extract their fluids. He also keeps Kerrie for his own purposes, but when Germain resists the idea, he is left on Eden.
Shortly after escaping the planet from Pitch Black, Riddick, Jack, and the Imam are picked up by a Mercenary spacecraft. Although Riddick attempts to conceal his identity from the mercenaries by impersonating William J. Johns (in Pitch Black) over the intercom, they quickly voice-print and identify him.
On a planet inhabited by Arachnids, a squad of soldiers find themselves pinned down and surrounded on all sides by Arachnid forces—even with their new laser gun technology and assistance from psychic soldiers, the Arachnid assault overwhelms them. General Jack Shepherd (Ed Lauter) decides to make a last stand with four of his best soldiers to allow the majority of his surviving troops to escape. The plan works and the soldiers escape, including Sergeant Dede Rake (Brenda Strong), psychic Lieutenant Pavlov Dill (Lawrence Monoson), Private Jill Sandee (Sandrine Holt) and her lover Private Duff Horton (Jason-Shane Scott), and Private Lei Sahara (Colleen Porch). Despite reaching relative safety, the team is whittled down by deadly storms and arachnid ambushes—including the only member of the platoon with a radio, Corporal Thom Kobe (Brian Tee). Lieutenant Dill is unable to command his soldiers as he receives traumatic visions of utter annihilation. He takes his anger out on Private Sahara, who is revealed to have been psychic but lost reliable control of her psychic abilities during puberty.
Alors que la guerre contre les arachnides fait rage, le général Johnny Rico est rétrogradé au rang de colonel et envoyé sur Mars entraîner un groupe de nouvelles recrues pour avoir laissé une reine arachnide atteindre la Terre. Pendant que la Fédération attaque la planète mère des insectes, ces derniers envahissent Mars, menaçant la Terre et plongeant l'équipe du colonel Rico au coeur de l'action. Mais les Arachnides ne sont pas la seule menace qui pèse sur la planète rouge...