After the very disappointing take (Wolf Man) by Leigh Whannell, which I watched recently, I had fairly low expectations for this film because it had much the same theme. Despite being a werewolf story, it was about how scary it is when some sickness or condition (lycanthropy, in this case) can make someone you love and who's supposed to protect you a danger to you.

It might be the modern day but Willow (Ashleigh Cummings), a girl of about 10 or 11, looks like she lives an off the grid farming lifestyle with her parents Noah (Kit Harington) and Imogene (Ashleigh Cummings), with Imogene's father Waylon (James Cosmo) living nearby.

Willow helps tend to the farming tasks that need doing around the property deep in forested countryside somewhere in England, but she's getting increasingly curious about the secret her parents have kept from her all her life.

Every night – during which she's forbidden to leave the house – her mother takes her increasingly irate father away somewhere, and when Willow follows them one night, she sees what happens. Imogene takes Noah to a dank clearing, locks him up with a heavy lock around his neck and stands back to watch him spout hair and fangs, his face extending into a muzzle and his body transforming into a shaggy wolf-like creature that apparently only wants to escape and kill.

Waylon couldn't disagree more with the way her parents have Willow living, and can see that she's eventually not going to listen when her mother hisses at her to get back inside to bed for much longer.

But Imogene tries desperately to maintain the status quo, locking Noah away from them all during the night and hoping it all goes okay.

But Waylon is right, and Willow's at an age where she's becoming much more critical, wanting to know what's wrong with her father. The tensions between everyone rises as she discovers more about what's going on, and thanks to what she's seen, it can only end in bloodshed and violence.

Then, in a very subtle and accomplished final scene reveal, we discover what might be the ultimate truth behind the whole story, something that's even more heartbreaking than what you think's been going on (but which I won't spoil here).

It has a lot in common with Wolf Man in that it's set deep in the wild, and a lot of it's very dark and colourless on screen, with a look the cinematography was obviously designed to make moody but which only really comes across as muddy, dour and at times very hard to see.

Along with dialogue, action and locations that are similarly low key and unobtrusive, it might have been a quite dull movie to watch, but one thing makes it a unique pleasure, and that's Ashleigh Cummings as Willow.

She's so expressive and so restrained when the scene calls for it, adjusting her register for exactly the emotional timbre whether it's happiness, fear or sadness, with more talent in one fingernail than plenty of grown up actors manage across an entire career.

She comes across as both the cutest, most vulnerable little girl you'd ever want in your family as well as someone smart and accomplished beyond her years.

I remember bring so struck by Ella Purnell in Never Let Me Go and being willing to watch anything else she's been in ever since, and I felt the same way about the ethereally skilled Cummings here.