Kaz can see everyone's double helixes with his bare eyes.
His friend's quintuple helix has been used in the "Controllable" genetic mutation experiment. As more and more people willingly undergo the procedure, the mutations evolve beyond anyone's control. Kaz crosses paths with Rebecca, whose parents are believed to have started the mutations.
Together with the bearers of the quintuple bloodline, they must stop the mutations from turning every citizen into permanent hybrids before humanity is lost forever.