Welcome to the world of Captain Saul Harris and Corporal Carrie Welles. They are soldiers enlisted in the United National Forces, which consists of two divisions: Earth Duty and Space Duty. The UNF was created to not only protect the Earth, but oversee and secure the space migration. Human populations now dwell on the many stations floating off Earth, the five colony settlements based on the Moon, and the developing colonies on Mars – the new frontier. The ‘UNF Space Zone’ covers the entire area of inhabited space as controlled by the UNF. This is the world that Harris and Carrie have sworn to do their duty and protect.