Few worlds in the universe are as perfect as the planet Eos. Little wonder that humans have settled there. But so have the Gorgons, a race resembling the Medusa of Greek mythology, who don’t want to share it with anyone.

Hating all things human, the Gorgons attack the human colonies, slaughtering. Outnumbered and out-gunned, the colonists call for help from the Interstellar Association of Worlds, which sends hundreds of ships and a hundred thousand Marines to aid them.

Sergeant Lion Biyela is one of those Marines, leading his team into battle. Even though he has fought in the worst of it, Lion manages to hold onto his humanity. But he is beginning to wonder if it is all worth it.

Wearing armored spacesuits, with personal force fields and carrying plasma rifles capable of incinerating anything and everything, Lion and his Marines scoot into battle on individual flying discs. The problem is, the Gorgons also wear armored suits, also possess personal energy shields, and also carry plasma rifles of equal destructive ability. But they don’t have flying discs.

When Lion’s team occupies an outpost in the ruined city of Belden, they are attacked by hundreds of Gorgons. He orders a retreat, but he and another Marine are cut off from the others. They soon discover their suits are infected with an alien machine virus. Their systems begin failing and they lose contact with the rest of their team.

Abandoning their suits, they are forced to flee on foot. Wandering into the subway tunnels beneath the city, they come upon a handful of survivors. The survivors hope Lion and his companion can rescue them, but they cannot. They must get back to their company and report on the machine virus and let their commanders know of the survivors’ location.