The film expertly and chillingly blends the very real horrors of fleeing a war-torn country with the tropes of the haunted house genre, telling a moving and incredibly anxiety-inducing story of a refugee couple's difficulties adjusting to life in the UK – and their difficult encounters with unwelcoming locals and coldly bureaucratic authorities.
There are many films that mark the film out as an incredibly exciting debut – and one of those standout aspects is the performances by the cast.
Read on for everything you need to know about the actors involved, including who they are playing and where you might have seen them before.
Wunmi Mosaku plays Rial Majur
Who is Rial? Rial has fled South Sudan with her husband Bol and daughter Nyagak, and is finding it difficult to adjust to the new environment – not helped by the grim accommodation in which she's been forced to live in and the supernatural forces apparently present.
Mosaku said playing the character: "I’m not one for horror films at all, I’m a scaredy cat. But I loved the script and I had never read anything like it.
"There’s something so special about this film, the emotional journey. The truth is the scariest thing.
"Rial’s strength and fearlessness was so attractive to me. She has wit and composure; she has a depth of understanding and a well of humanity. She’s not afraid to look the truth in the face, her own or anybody else’s. Her pain doesn’t frighten her.”
What else has Wunmi Mosaku been in? Mosaku was recently part of the main cast on another project that used horror as a means of exploring contemporary issues - HBO's series Lovecraft Country. Previous credits include Black Mirror, Vera and the fifth season of Luther, while on the big screen she has had small roles in Batman v Superman: Dawn of Justice and Fantastic Beasts and Where to Find Them.
Ṣọpẹ Dìrísù plays Bol Majur
Who is Bol? Rial's husband, Bol seems determined to adapt to UK life – buying new clothes and watching football in the pub - while attempting to block out his past trauma but is also haunted by the supernatural forces in the house.
Dìrísù said of the character: "I think Bol is a really interesting study in masculinity, especially traditional views on what it means to be a man in a lot of African cultures – the expectation to be the leader, protector; to be fearless.
“We know now that stripping people of their ‘traditional gender roles’ frees them and makes for a better society, but many people aren’t at that stage yet, and Bol is one of them.
"It was really interesting to get into the mind of this man who was so desperate to survive in his new surroundings, unable to allow himself to ask for help or confide in his partner, and who ultimately makes headstrong decisions that hinder rather than help.”
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What else has Ṣọpẹ Dìrísù been in? Dìrísù had a high profile role as Elliot on Sky Drama series Gangs of London earlier this year, while earlier TV appearances included Humans and The Halcyon.
Matt Smith plays Mark
Who is Mark? Mark is Rial and Bol's caseworker – who claims to have found them a 'palace' to live in, although it turns out to be far from ideal living conditions.
Smith said of the character: "I liked the normality of Mark in a world that was seemingly abnormal.
"And the ambiguity of Mark is something that was very interesting to play – his own jealousies and self-interests, coupled with his genuine concern at seeing others human beings avoid suffering, and to progress in a new world. He had a job to do: house people.”
What else has Matt Smith been in? Smith won't need any introduction to most telly fans – he played the eleventh Doctor on beloved sci-fi series Doctor Who, and more recently starred as Prince Phillip in the first two series of The Crown. Previous film credits include Terminator Genisys while he is set to star in Edgar Wright's next film Last Night in Soho and Spider-Man spin-off Morbius.
Malaika Wakoli-Abigaba plays Nyagak
Who is Nyagak? Nyagak is Rial and Bol's daughter, who tragically dies while the family are fleeing war-torn South Sudan.
What else has Malaika Wakoli-Abigaba been in? This is Wakoli-Abigaba's first major on-screen appearance.
Emily Taaffe plays Dr. Hayes
Who is Dr. Hayes? Dr. Hayes is a doctor at the nearby surgery with whom Rial has an appointment.
What else has Emily Taafe been in? Taafe has appeared in supporting roles on a number of TV series, including Ripper Street, New Tricks, Call the Midwife, Atlantis, Death in Paradise, Informer and Vera.
Javier Botet plays The Witch and Cornell John plays the voice of The Witch
Who is The Witch? The Witch appears to have followed the couple from South Sudan, continuing to haunt them in a number of ways.
What else has Javier Botet been in? Botet has history for playing otherworldly creatures – with a number of high-profile credits including Crimson Peak, It, The Conjuring 2, The Mummy, Slender Man, Mama and the REC franchise.
What else has Cornell John been in? John is best known for his role as Curtis in the film's Kidulthood, Adulthood and Brotherhood while he also briefly appeared in EastEnders in 2013.