Twenty-five-year old Susanne (Almudena Amor) enjoys a stylish lifestyle as a publicity model in Paris. One evening, just as she is about to start a new gig, she receives a phone call informing her that her grandmother Pilar (Vera Valdez) has suffered a brain hemorrhage. Susanne is Pilar’s only living relative, her parents having passed away in a car crash years earlier. She is urged to fly back to her native Madrid in order to care for the older lady, who is left completely silent and unable to look after herself. Susanne feeds, washes and attempts to talk to her grandmother, despite being told that her state is irreversible. Caring for someone in such state is neither easy nor pretty. Susanne’s life has suddenly turned from glam to gloom.

Pilar’s figure is the subject of nightmares: her body is scrawny and wrinkly, her face demonic, with pearly black eyes, shrunken lips and mouth wide open most of the time. Her gaze is completely empty. A frustrated Susanne tells her: “you are no longer there, are you?” The old lazy does however walk around the house unaided, often appearing in very unexpected places.

Short flashbacks and portraits on the walls suggest that Pilar had a hedonistic youth, and that she was just as fashionable as her granddaughter. Susanne finds her childhood diary with disturbing drawings. A neighbour called Eva (Karina Kolokolchykova) reveals that their grandmothers were best friends, and that they (Eva and Susanne) used to play together as kids. Susanne has no such recollection. Gradually, strange little events bordering on the paranormal begin to take place: a door mysteriously shuts, then lights flicker, grandma is magically transported from one room to the next. Susanne has horrific nightmares that eventually morph into reality. And so she begins to questions her very own mental health.

The balance between the visuals and the pace of the narrative is just right. The genre devices build up slowly but surely. The movie borrows a couple of clever ruses from horror classic The Skeleton Key (Iain Softley, 2005), except that Kolokolchykova is far less talkative than Gena Rowlands’s character. The ending is wonderfully extravagant, with a fabulous twist which will force you to revisit the movie and put the puzzle pieces together as you walk back home from the movie theatre. Just like any horror with an effective script should.

The Spanish director Paco Plaza is best remembered for the three [Rec] movies (2007, 2009 and 2012), which he wrote and co-directed. He continued to hone his horror skills with the commercial hit Veronica (2017), and he has now inserted further flare and subtleties into the genre, with this highly effective flick guaranteed to please his fans and convert new enthusiasts.

The Grandmother premiered in the Official Competition the 69th San Sebastian International Film Festival. It’s rather unusual for such A-category festivals to pick horror movies, particularly for their most prestigious section. This finely-crafted Spanish-French co-production, however, is welcome addition to their selection.

The UK premiere takes place in October at the BFI London Film Festival.