Free with Sky Cinema or £7.99 to rent on Amazon Prime or YouTube.
I thoroughly enjoyed this, even on a superficial level I found it full of the tension, surprises and scares any decent horror type thriller should have before considering deeper meanings. The most obvious being allegorical. A tale mirroring the difference in society between 'the normal' better off leading a 'happy' existence full of possibilities and the oppressed, depressed 'others'- the tethered - leading a miserable limited existence with no prospects and no real life. A deliberate pointer imo towards US society in general, and the great divide between the middle class and oppressed, the haves and have nots as it is between the oppression of races, a problem America especially has been torn apart by for generations upon generations and is right front and centre of the news right now.
(There are nods to other past horror films notably The Shining and others which may have influenced the writer)
**** Warning minor spoiler below *****"
Again there's a neat twist right at the end which recalls the very start of the film and the hall of mirrors, who actually is the now grown up wife after all?