Brander, the security chief of the Syrtis Base on Mars, isolates the entire emplacement when two men die from an unknown, alien disease. No one can enter or leave the base. Dr. John Naysmith, newly arrived on Mars, leads the medical team desperately trying to discover a serum to combat the virus. If they can't contain the spread of the disease Brander must annihilate the base and everyone in it with nuclear bombs! Then another three men become infected ...