Back in 1957, in the quiet village of Langho, Lancashire, three young sisters were found dead in bed.
Dressed in their pyjamas, Sandra, Yvonne and Moira Marshall — aged ten, nine and five — were lying beneath a carefully arranged canopy of sheets and blankets. Of their mother and father, there was no sign.
Police had been alerted by a call from the girls’ grandmother, who’d received a frightening letter from their mother Elsie saying, ‘The children are sleeping peacefully’
