After three years away, seventeen-year-old Brodie McKellon has returned to live with her eccentric grandmother above the last remaining Dead Letter Office - the place letters go when no one is left to claim them.

Soon, Brodie is consumed by an unsolved mystery - the unclaimed letters of a group of teens who seemed to vanish many years ago - while also attempting to reconcile with her former best friends, Elliot and Levi.

As the trio is 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 . . .