In the year 2019, a plague has transformed the majority of the world's population into vampires. As the human population nears extinction, vampires must capture and farm every remaining human, or find a blood substitute before time runs out. However, the lack of human blood causes panic and desperation among vampires, leading to the decline of their structured society and the emergence of feral vampires called "subsiders," who are unable to get enough human blood to maintain their sanity. Edward Dalton, a vampire hematologist, is repulsed by the thought of vampirism and is working on a blood substitute, motivated by a lingering sense of humanity.

Dalton's work is marked by the pressure from vampiric society, particularly from Charles Bromley, the head of a powerful pharmaceutical company, who sees the blood shortage as an opportunity for profit. An unexpected encounter with a group of humans turns Dalton's life upside down, introducing him to a possible cure for vampirism. This discovery sets Dalton on a dangerous path, as he becomes torn between the vampire authority that demands suppression of the cure and his own ethical compass that drives him to do the right thing for humanity's survivors. Dalton faces a race against time, as the prospect of a solution to the blood crisis offers a glimmer of hope amid the darkness that has enveloped the world.