Dear Amy

Margot Lewis is the agony aunt for The Cambridge Examiner. Her advice column, Dear Amy, gets all kinds of letters - but none like the one she's just received:

Dear Amy,
I don't know where I am. I've been kidnapped and am being held prisoner by a strange man. I'm afraid he'll kill me.
Please help me soon,
Bethan Avery
Bethan Avery has been missing for nearly two decades. This is surely some cruel hoax. But, as more letters arrive, they contain information that was never made public. How is this happening? Answering this question will cost Margot everything...