Watch for Me by Twilight — Kirsty Ferry

Moving between the present day and 1930s England, this compelling, romantic mystery reminds us that the past is never really the past . . .
 
Aidan Edwards has always been fascinated by the life of his great-great-uncle Robert. A trip to Hartsford Hall, and an encounter with Cassie Aldrich, leads him closer to the truth about Robert Edwards, as he unravels the scandalous story of a bright young poet and a beautiful spirited aristocrat in the carefree twilight of the 1930s before the Second World War.
 
But can Aidan find out what happened to Robert after the war -- or will he have to accept that certain parts of his uncle's life will remain forever shrouded in mystery?
 
The Hartsford Mysteries series can be read in any order.