This sounds like an almost perfect plot - a family mystery that becomes an obsession - an old castle, of which Scotland has many, all of them with old mysteries! The wild arctic to explore, as shown in the dramatic front cover image which captured my attention straight away is another of Elizabeth's skilful "tricks" to draw you in. The period, 1949, had no mobile phones or internet, so all the clues have to be found by brain power and worked through with thoroughness. I like it!