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.

They leave when everyone is asleep. On the surface, in the dark, looking for a safe refuge, they are attacked by an unarmored Gorgon, who nearly kills them. After killing it with chunks of rubble, they stumbled into a shattered building.

While Lion rests, his companion is attacked by human scavengers, whom he mortally wounds. When Lion awakens, he discovers his friend injured and unconscious. He cannot leave his Marine to die alone, so he carries him on his shoulders, moving at night, avoiding enemy patrols. After many terrifying days, they reach friendly lines.

Awakening on an orbiting hospital ship, Lion finds he cannot remember what happened after his suit failed. While his Marine recovers from his wounds, Lion returns to active duty.

What’s left of Lion’s team is assigned to protect a Marine major’s patrol. The major’s mission is to capture enemy officers. As they proceed back into Belden, the major bullies Lion about the survivors. But Lion has no memory them. The major’s accusations keep Lion on edge.

After days of searching for enemy troops, they finally locate them. While sneaking into position to capture their prey, the major reveals he ordered Lion’s memories of the survivors deleted. The major reveals he stole Lion’s memories to further his career, taking credit for the survivors’ rescue. Lion is furious.

During the battle for prisoners, the major restrains Lion while using his team as bait. When two of Lion’s Marines fall, he escapes and rescues his remaining Marines. The major captures his prisoners, at great cost to his own troops. Everyone returns to safety, whole if not happy.

Months later, as the Gorgons retreat, Lion’s battalion pursues them. After chasing them for seven hundred kilometers, Lion and his battalion reach the Axial River, which stretches thousands of kilometers to the east. Here they fight for the bridge over the great river. The Marines, with flying discs, don’t need the bridge. But the colonists’ armed forces do.

The battle is brutal. Only thirteen members of Lion’s forty-two Marine platoon, survive. So many friends have died and he wonders why any of this fighting is necessary. After a year of fighting, was it worth it?