What it is to be human doesn't apply anymore. The surface of the Earth has been poisoned by years of abuse and now most life lives beneath the waves of the ocean. Over the last 500 years, humans have become fragmented and specialized by genetic manipulation, but two main factions exist in the Undersea. The hybrids, a race that continues to genetically modify themselves to climb the social ladder, and the humans, the unmodified organic race that makes up the lowest tier of society.
Alex, a Delta Six hybrid, finds an unlikely companion in a human man, Jack, while on a mission to steal the Athena file. Alex withholds the file to elicit help from Jack and they set out on an adventure across the Surface. Their relationship is tenuous until a device mysteriously links them together. Now, running from Alphas, an elite group of hybrid assassins, Alex and Jack must weather the hostile surface of the planet to reach their common goal. They soon find they can't both have the thing they want most, but also can't seem to let each other go.