Like many teenagers in her town, Quinn Larson awaits her eighteenth birthday with equal parts excitement and dread. Every person who turns eighteen gets the opportunity to travel to their past, present, or future, which can drastically alter their view of life, for good or ill. A red serum is injected into willing arms and immediately transports the teens to the jumping point of their choosing. The jumpers can see who they marry, what job they have, better understand a current problem, or relive a significant moment in their childhood.

Quinn is also a worker at the Care Centre, where people go after their jumps to try and process what they have seen. She knows that not everyone has a happy ending, and they must live with the pressure of a past they can't forget, a present they are avoiding, or a future they can't reach.

When one of Quinn's dearest friends, Graham, returns from his jump drastically changed and jumps begin to fall into chaos, she knows she has to take matters into her own hands to return him to his former self. With jumpers being pulled out of existence, Quinn is forced to break all sorts of rules to save Graham and all future jumpers.