Cragside.
(Adult Book, Reference)

After his climactic battle with notorious serial killer The Hacker, DCI Ryan is spending the summer with his fiancée within the grounds of Cragside, a spectacular Bavarian-style mansion surrounded by acres of woodland. When they are invited to attend the staff summer party – a Victorian murder mystery evening – it’s all a joke until the lights go out and an elderly man is found dead. It looks like an unfortunate accident but, as the dead man’s life begins to unfold, Ryan and his team of detectives realise that all is not as it appears.