After years of drifting between jobs, Karl has finally found the one – working for the local council to help ghosts pass on to the afterlife. Mentored by Archie, a curmudgeonly old man, Karl begins to learn his trade.  Karl's life is finally going well, but all of this is threatened when a routine exorcism goes wrong.

While Archie lies in hospital, Karl is horrified as their work colleagues attempt to kill Archie. Karl discovers Archie has not told him everything – about their job, about his life. Karl learns about The Lost: a confluence of spirits using the recently deceased to force their way back into the world. Archie's colleagues believe Archie's coma provides the bridge for The Lost to return to the living world. As Archie lies dying, can Karl trust his friends to protect Archie and find a way to save him before he is lost?