Subject-07, A&B live on a small planet with low gravity, a cool climate and a thin atmosphere. Their solar system is a crowded place with multiple worlds and many life forms. The subjects coexist within an unusual symbiotic relationship involving one residing inside the other's head. The creature' living within is a parasitic life form and a highly evolved virus that has become sentient after millions of mutations. Its host is a low intelligence but formidable creature with high stamina, strength and perseverance, the perfect evolutionary tool to propagate. The parasite is mostly in control of the host's thoughts and actions. However, it will eventually kill it and has already decimated the population. The virus has recently contrived a plan to spread to another world by hitching a ride on a mining ship that landed on the planet. The miners are unaware the virus is living in the indigenous population. If it's successful, it will surely infect the miners and spread to their world.