The problem of dwindling supplies of Plutonite is solved when an asteroid made of the material is discovered. But before Raeburn has managed to secure the asteroid Miga, a wealthy Venusian has taken possession and intends to sell it. Raeburn reluctantly agrees to the asking price and sends Dart to complete the transaction

Professor Borra of Venus has invented a mechanical eye which can destroy any ship constructed of metal alien to Earth, Mars or Venus. The demonstration is impressive but what will happen when a Galasphere constructed from metal mined from Pluto comes within range?

Exploring the Silver Forest of Venus, Husky becomes trapped in the web of a Spirigum Spider. Haggarty manages to free him and discovers that fragments of the web act as a truth drug. Raeburn, meanwhile, is offered the formula for Kinotine, which has the ability to store heat indefinitely. Kinotine's inventor, Dr. Mason, will donate the formula but when a call is received from Kolig, head of Mars's largest chemical plant, offering the formula for sale, Raeburn suspects foul play

Haggarty invents a robot that responds to thoughts. Dart tests the range of telepathic thought in space and investigates a new planet near the Sun unaware that the Neptunians have encamped there. Only Haggarty's new robot escapes the Neptunians' hypnotic influence

A strange jittering is affecting the city and other Earth locations. Haggarty discovers, by chance, that the jittering is caused by radio waves emitted by Uranus, where the Duos are once again planning an invasion

Tyrig plans to use a nerve gas to seize power on Mars. Raeburn discovers that Tyrig and his men have set up base on the Martian moon Phobos and Dart is sent to investigate. Dart and his crew are captured by Tyrig, who wants to use the Galasphere to spread the gas. Refusing to co-operate they are placed in a dungeon which slowly fills with sand

The Galasphere's Meson unit malfunctions and lands in the unexplored Tuhera jungle. Dart and Husky leave to fix the problem. When Husky fails to return, Dart follows and is captured by a giant primitive man. Husky speaks with the giant in its native language and they are set free. They return to Earth with some Martian fruit which makes hair grow—the perfect solution to Haggarty's problem

Saturn has a new leader. Riga is succeeded by his brother Simba and whilst Dart is en route to investigate, Simba launches rockets destined for Earth containing Saturnian grass seed—which absorbs oxygen and emits carbon dioxide

The Neptunians create a forcefield around the Earth containing particles with strong electromagnetic properties. The field begins disrupting electricity supplies, causing a complete blackout

The Galasphere is sent on a rain-making mission to Mars with a cargo of oxygen and hydrogen—the very ingredients escaped criminal Marog requires to complete his bomb under construction at his Phobos hideaway

Raeburn is contacted by Yria from Alpha Centauri who is seeking help to destroy an evil computer superbrain which is attempting to take over the planet Delta

On a mission to Jupiter, Slim disappears in the swamps. Raeburn orders Dart and Husky to leave but trouble with the Galasphere's primary drives gives Dart an excuse to resume the search only to find that Slim has shrunk to dwarf-like proportions