For years, Declan "Dex" Breen has lived on the wrong side of the law, chasing his pleasures whenever and however he can. But in the wake of a devastating accident, he finds himself with a mangled leg, and temporarily bound to a mobility scooter-haunted by feelings of boredom and worthlessness and ready to make a change.

So in order to escape his unsavory past, Dex decides to volunteer his time to the Guardians, a local telephone crisis hotline, as soon as his health will allow it. In the meantime, he deals with his restlessness by taking rides around the neighborhood on his mobility scooter-a habit that introduces him to local martial arts instructor Moira Clark.

As Dex works toward completing his Guardians training, his bond with Moira soon expands to include psychotherapist Suzanne Lindstrom, a fellow volunteer. But when the trio is suddenly drawn into a disturbing local murder investigation, loyalties are tested and the complexities of their friendship are called into question as the dark truth behind a series of murdered high school students finally begins to surface.