A journalist and an archaeologist go to Africa and find an atomically mutated giant ant with super-intelligence. The giant ant tries to lead an army of insects to world conquest, but is foiled when the humans use sugar to turn his ants against him.; A subway train full of people is hijacked and held by a subterranean race. The police fight the creatures and retrieve the train, only to discover that the creatures were actually peaceful.; A robot is sent to Earth by alien conquerers to force them to surrender or be destroyed. The finer qualities of humanity convince the robot decides to destroy his creators' world instead.; A scientist builds a time machine and uses it to travel into the future against the advice of his peers. He finds that time is an infinite loop, and when he reaches his own time his memories disappear and he is once more building a time machine.