Fifteen-year-old Seth Rosenberg has just entered his freshman year of high school--isolated, friendless, and eager to have the next three years pass him by as swiftly as possible. But when Wynter Meadows, the widely popular, not to mention Seth's biggest crush, reveals that she is in the midst of a battle against leukemia, his entire world is flipped upside down.

Seeing that Seth is the only student to know of Wynter's condition, the two of them end up forming an unlikely yet secret friendship. During which, Seth learns that Wynter has chosen not to treat her disease and, consequentially, has been given less than a year to live.

With the monumentally important task of changing Wynter's mind weighing heavily on him, Seth must deal with the intense roller-coaster ride that accompanies being friends with Wynter Meadows while also being painfully aware of the unfortunate reality that awaits if he is to fail his mission.