The year is 2099, and Freddie Molloy - a young man whose DNA was forcibly altered in a manner that affects his life to this day - works as a geneticist alongside his father. While his timid father Martin is the chief of their department, he is not the boss. That title is reserved for their current patron: Mr. Travis York, a multi-millionaire employing the genetics department to make him an ace in the hole for his mayoral candidacy.
The terms of their accord are simple: they have to make him a serum that grants the user fins, amphibious lungs, and scales: everything humanity would need to reclaim the territory presently barred by the flooded sea levels. If they succeed, Mr. York will give them all the funding they could ever need. But if they fail, their department will be shut down and all of them will be fired. And in this world, being fired is the first stumble in a slippery slope that leads to death. They have been trying for weeks, but have nothing to show for it but a bunch of mutants who die within the week. Martin is terrified of both the prospect of losing his job and of his superior, whose kind effectively rule the world. Freddie is more annoyed than anything else, but his mood improves when he goes out to steal some pricey foodstuffs destined for the super-rich. Since the wealthy have taken so much from him, he deems it fair that he return the favor.
When he goes out to the beach, however, he encounters something far more extraordinary than a few exotic treats. He hears, and is smitted by, the song of a siren: a seductive (even for asexual Freddie) yet vicious carnivore who's willing to risk the acidic waters near the city just to get her meal. But she draws too close, and it is this desperate hunger that gets her confined in a tank and made into an asset for the genetic department's goals. Up until now, they've been lacking the DNA of a creature that could bridge the gap between 'human' and 'fish'. And now, they have it.
Freddie is made into the mermaid's handler, seeing as she spared his life and sees him as kin due to his genetic mutation. What started out as a job slowly develops into a deep bond, to the point that Freddie sheds his professionalism and names the mermaid 'Perdita'. He teaches her of his world, and she teaches him about hers. But with every day that passes, Perdita grows weaker in her tank, and Mr. York grows more and more obsessed with using his mermaid to win the election.
That is when Freddie, with the help of his father, decides to do something akin to suicide in this world: go against the rich.
