Flint Larson has 41 days, 9 hours, and 42 minutes to live. He’s known exactly when he’s going to die since he was eight years old and half-lifed, a small twinge that tells a person when they’ve lived half their life. And from that moment, Flint’s done everything he can to make dying seem like a good thing. Cutting off all his friends, refusing to eat his favorite foods or listen to the best bands, reading only the most depressing literature by long-dead writers. He plans to spend his final days quietly back in his hometown with just his parents, waiting to die.

He did not expect to meet September Harrington, an utter explosion of brilliance and fun. September has dedicated herself to curing the half-life, landing a coveted internship at the world-renowned Half-Life Institute in town. September has her own past that she’s refusing to deal with, instead choosing to live up each moment either in the center of everything or deep in lab working with the best scientists, where she’s on the brink of finding a cure.

When their worlds collide, it’s like it’s meant to be. Only Flint can’t bring himself to tell September he’s dying, and September’s keeping secrets of her own. The closer they get, the less time they have together and the more their secrets threaten to destroy everything. Can September and Flint save each other, or are their days numbered from the start?