After three years away, Brodie McKellon has returned to Warwick to live with her eccentric grandmother above a Dead Letter Office - the place letters go when no one is left to claim them.
But with her reputation as a troublemaker, things don't stay quiet for long, and Brodie soon reunites with her childhood best friend, Elliot, and sidekick-turned-nemesis, Levi, to investigate an unsolved mystery: unclaimed letters from a group of friends who seemed to vanish without a trace nearly twenty years ago.
As Brodie, Elliot and Levi are drawn into the riddle of the dead letter writers, they discover that the past is never truly past, and that it's never too late for old wrongs to be put right.