The tired old dog of adaptations, The Hound of the Baskervilles has always been a bafflingly popular choice when it comes to pasting Sherlock onto the screen.

It’s one of the least exciting Holmes adventures, but every time it regenerates into a new form it draws people in. Why? Because they want to know what the dog looks like. The only problem is that when they finally see it, it’s usually disappointing.

Writer Mark Gatiss is clearly aware that the idea of the eponymous canine is always more terrifying than the sight of it, and that The Hound of the Baskervilles is at its core a psychological story, not a monster story. In being so aware of the power that the human imagination has to play in reading or watching the story, he has created a refreshing take on the tale with The Hounds of Baskerville.

Poor Henry Knight (Russell Tovey, escaping one kind of giant dog in Being Human only to be confronted by another here) begs Sherlock to investigate his father’s 20 year old murder by ‘a gigantic hound’. This takes Holmes and Watson to Dartmoor and the mysterious Baskerville biotech research compound, where experimentation knows no limit…

It’s a far less complex story than last week’s but no less exciting. A Scandal in Belgravia was a 3D jigsaw within a Cryptex, Hounds is a straightforward Rubik’s Cube: everything’s there, you just have to watch it twist into shape. As it does so fans of Batman Begins may find something very familiar, but of that we’ll say nothing more.

Dartmoor is magnificently shot by director Paul McGuigan and just as Henry Knight describes it: bleak but somehow beautiful in its bleakness. Scenes on the moors have a washed out quality to them that’s starkly juxtaposed with the bright lens-flare lit interior of the Baskerville labs. So accomplished is the cinematography, so sharp is the contrast between the visual textures of earthiness and sterility, that you may come away with whiplash of the eyes.

It’s a nice change to see Sherlock out of his concrete and steel comfort zone and pushed into unfamiliar territory – both geographically and psychologically. His heart was tested last week, this time it’s his head.

The impossible is eliminated, the terrifyingly improbable is left, and Benedict Cumberbatch once more gets to stretch Holmes past the icy intellect we know and into new areas of emotion that are as uncharted and frightening to the audience as they are to the detective.

Tovey does a great job as a man tormented by the trauma of the Hound. That jittery fear he perfected as George in Being Human is here translated into something more grown-up but equally harrowing.

Part detective story, part psychological horror, The Hounds of Baskerville is a different beast to every previous adaptation, but in being so it manages to show off what makes the original story so fascinating in the first place.

And the what of the star attraction, the Hound? Well, obviously you’re going to do what every Baskerville audience has always done and watch to find out for yourself…

Airs at 8.30pm on Sunday 8th January 2012 on BBC One.

> Order the Series 2 DVD on Amazon.

> Buy the Series 1 DVD on Amazon.

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