The farming world Akir is threatened by the tyrannical warlord Sador (John Saxon), who rules the sinister Malmori Empire and, his body parts deteriorating, is capturing and appropriating them from others. Sador's huge dreadnought, the Hammerhead, mounts a "Stellar Converter", a weapon that turns planets into small stars. He demands that the peaceful Akira submit to him when he returns in "seven risings of your red giant", or he will turn his Stellar Converter on their planet. Zed (Jeff Corey), last of the famous Akira Corsairs, is old and nearly blind. He suggests they hire mercenaries to protect their world. Since Akir lacks valuable resources, its people can offer only food and shelter in payment. Unable to go in person, Zed offers his ship for the job if they can find a pilot. The ship is fast and well-armed, but, despite its AI navigation/tactical computer Nell, cannot defeat Sador alone. Shad (Richard Thomas), a young man who has piloted the ship and is well known to Nell, volunteers for the recruiting mission.
Seeking weapons, Shad goes to the space station of Doctor Hephaestus (Sam Jaffe), an old friend of Zed. The station is populated mostly by androids, except for two humans: Hephaestus, whose numerous life support-systems have turned him into a cyborg, and his beautiful daughter Nanelia (Darlanne Fluegel), who looks after him and the androids. The doctor wants Shad to mate with his daughter, by force if necessary. Shad cannot bring himself to abandon his people; he persuades Nanelia to help him escape. She follows in her own ship; although she has no weapons, her highly advanced computer systems might be useful. The two split up to look for more mercenaries.
Shad encounters Cowboy (George Peppard), a freighter-pilot from Earth who is ambushed by Space Jackers while delivering a shipment of laser-handguns to the planet Umateal. Shad fights off the Jackers, thus saving Cowboy's life twice over; they arrive at Umateal just in time to watch Sador destroy the planet with his Stellar Converter. Lacking the fuel to carry his weapons back home, Cowboy offers them to Akir instead. Shad talks Cowboy into sharing his gunslinging experience with the Akira.
