The game takes place in an era of space colonization. Planet Earth, after a serious nuclear war between it's nations, formed a major government of the richest surviving governments and industries to explore space colonization, eventually settling a solar system outside of Sol. Alpha Centauri is a system with two planets, the lush and blossoming Vekta, the other rich in energy supply but inhospitable; Helghan. These two planets were purchased by the Helghan Corporation after the UCN (United Colonial Nations) decided to auction them. However, after Helghast's economic policies threatened to undermine the UCN's financial system the UCN invaded Vekta and removed the Helghast after failing to impose financial sanctions. This forced the Helghast to colonize Helghan, a harsh and brutal planet, and deeply resenting the loss of Vekta. The planet's harsh environment forced the Helghast to adapt and mutate so much that they can no longer be considered human. They are stronger, faster and more resilient than their human cousins, and possess a burning hatred for humanity. Except for a small number of half-breed Helghast and trained troopers, they require a gas mask and air processing tank.
Plot. The Helghast are a faction of human descendants that were banished from the planet of Vekta to the brutal and harsh planet of Helghan many generations ago. The Helghan Empire recovered from it's defeat in the First Extrasolar War and were united under the leadership of their nation's Emperor, Scolar Visari. Under the guidance of Visari, the Helghast launched a blitzkrieg campaign against the neighboring planet of Vekta. An ISA soldier named Captain Jan Templar fights against the Helghast invasion, but the ISA suffers heavy losses with the imminent invasion. As Templar and the rest of the ISA retreats, he meets up with other allies such as Shadow Marshal Luger (a female special ops assassin), Hakha (a half Helgast half Human spy) and Ricardo "Rico" Velasquez (a trigger happy ISA soldier), and together they set out to repel the invasion. However, there is a traitor in the ISA who actually let the Helghast into Vekta.