Robbie's ship is caught in a gravity field while searching for a missing vessel in another stellar system. Buzz and Happy race to his rescue only to be trapped also. Can they escape Arachna's web before the Terra-5 is stripped and melted for its component metals?

Having once escaped, Buzz, Happy, and Robbie must return to Arachna's ring-shapped planet to rescue the remaining prisoners. Disguised as an old miner, Corry again allows himself to be caught in the gravity web but is quickly unmasked by Arachna. Can the commander and his men still complete their perilous mission?

Handcuffed, Arachna momentarily escapes custody and sabotages the Terra-5. Buzz manages to recapture him and blast off in the decoy ship before the ring planet collapses. But will Corry manage to rescue his own ship and its passengers before they are destroyed?

Commander Corry orders Happy to take Major Robertson and the rescued slaves back to Terra while he remains on board a crippled alien spacecraft with a beautiful girl who is in a coma. After Happy takes off, Buzz discovers that the young woman was feigning unconsciousness when she blasts him with his own ray gun. The woman, Yula, and her confederate, Raymo, have created a process where they can replicate any human as an android and, with Corry safely locked away, plan to send his duplicate to Terra to lure the Secretary General to a phony peace conference so they can capture and replicate him.

Yula aids Raymo to escape. Together with the duplicates of Corry and the Secretary General, they blast off for Terra leaving Buzz, Happy, and the real Secretary General trapped behind an electric barrier. Can Buzz and his friends escape in time to prevent the take over of the United Planets?

Yula and her androids, all of whom look like persons occupying key positions in the Federation of Planets, have invaded Terra. Corry and Happy think they've captured the last of them, only to discover that the "ringleader" is really an android of Yula. The real Yula blasts the Space Patrol officers with her ray gun and escapes to create more replicants. Soon androids resembling the Secretary General and chief of Security give orders to capture or kill Corry and Happy on sight and Corry must devise a plan to capture Yula before her androids take over the Solar System.

Commander Corry and his crew investigate a mysterious burst of radiation from outside the Solar System. They trace the source to the surface of a planet whose once great civilization has been recently devastated by nuclear war. When they approach a space station above the planet's surface to search for survivors, their spacecraft is seriously damaged by a bomb and forced to land on the planet's charred surface. While attempting to repair their ship in the unbearable heat, their remaining water supply is stolen by two of the holocaust's survivors.

With the Terra-5 finally repaired and ready to take off from Procyon, Happy and Carol suddenly disappear. Will Buzz and Robbie be able to locate their friends and safely escape the war-ravaged planet?