The Skull

In "The Variable Man", Earth (The Terran System) is in a cold war with the older, corrupt Centaurian System, which suppresses Terra from exploring space and expanding its borders. When a devastating new weapon called Icarus is developed by Terra, everyone expects the odds to tip in Terra's favor. But the computers calculating these odds find an unknown variable that throws off the odds. A time traveler from 1913 known as Thomas Cole has arrived. Can this variable man from the past rescue mankind from a catastrophic future?

In "The Gun", a group of space explorers are shot down above a deserted planet. While some of the crew work on repairing the ship, the remainder set out to investigate the planet. Otherwise unpopulated, they discover the huge gun that shot them down sitting atop a trove of cultural artifacts from a bygone civilization. What harm could come of dismantling the gun and taking a few of the artifacts home with them?

In The Defenders, the Soviet and American survivors of a nuclear holocaust have created vast underground tunnels, so as to continue the war on the surface via remote control robots. When a robot from the surface is found not to be radioactive, a team of American scientists returns topside to investigate this anomaly. Expecting to see massive devastation, the scientists are unprepared for the shocking truth that awaits them.

UN forces have retreated to a moon base in the aftermath of early Soviet victories in a nuclear conflict. In response, the UN forces developed special robots, called "Claws", which feature spinning blades and rudimentary artificial intelligence. Six years later, the Soviet leadership asks for negotiations to end the war. A UN officer travels back to earth to discover that not only have the Claws learned to replicate themselves, they have also created a much deadlier cyborg that threatens humanity itself.

In "The Crystal Crypt", Earth and Mars are poised on the verge of war. On the last spaceship to leave Mars for Earth, law enforcement officials are looking for three fugitives who somehow made a great Martian city disappear. Unable to find the perpetrators, the officials allow the ship to disembark for Earth. A businessman named Thacher strikes up a conversation with a young woman and two men who reveal a very interesting secret to him about the mysterious case.