In a world where various plant seeds are cultivated for unique purposes—such as to instantly start fires, create materials similar to rope, or send signals from a distance—rare seeds are sought after. In order to maintain economic and political stability, the National Grainelier Special Education and Research Institute holds exclusive rights to grow and research seeds and also polices the use of seeds that can be ingested by humans. These seeds transform people into "carriers," making them more similar to plants than humans and granting them dangerous powers.

Following the death of his mother, Luca Anglade lives alone with his reclusive father Christophe. Both father and son illegally grow seeds, but whereas Luca sells his seeds in order to afford their living expenses, the goal of Christophe's experiments is a mystery. One night, a Grainelier security team arrives and attempts to arrest Christophe. He commands Luca to swallow a handful of seeds and then flee, but Luca is barely able to get a safe distance away before losing consciousness. When he wakes up, he finds himself in the home of his childhood friend, Abel Guivarch, who informs him that two years have passed—but Luca does not appear to have aged a day since that fateful night.