A real mystery for you, as we head to Scotland for the case of Bible John, an unknown serial killer who raped and murdered 3 women between 1968-1969. Apart from their physical similarities and the MO there was one alarming point to note, all the women were menstruating on the nights they were attacked. How did he know? What did it have to do with anything? And crucially, who was he? We have some theories...

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