There's a flavour of MR James-style English uncanny to this supernatural tale. It has all the ingredients – a gloomy country house, things that clatter in the night, and an academic (Ed Stoppard) who increasingly veers off the rational rails. There's also a dash of the Spanish/Mexican chiller school, with a mysterious masked child who might have stepped out of The Orphanage. It's all done in a business-like, precisely managed fashion, director Adam Wimpenny and writer JS Hill building up to their climactic twist with elegance and rigour. But it's a twist I've seen pulled before, and even if you've never come across it, I doubt it'll quite induce the intended frisson. So trad it could have been made in the 60s, Blackwood nevertheless has the courage of its old-school convictions.