In the 21st century, mankind has finally made contact with intelligent life forms from another planet. Alas, the aliens are hostile. First they invade Mars, usurping all of mankind's space stations and annihilating their crews. They plan to use the red planet as a launching pad for their sweeping attack on Earth. The future of human civilization is in the hands of space Cmdr. Mike Halstead (Tony Russel) and his intrepid crew, the last line of defense between the aliens and Earth.