Don’t let his looks deceive. This titular terror may initially strike you as intimidating, with his towering height, fiery eyes and ferocious voice. But fear not, for he isn’t here to harm, he’s here to heal.

The Monster (Liam Neeson, at once compassionate and contentious) first appears to young Conor (Lewis MacDougall) in the dead of night. Though taller, he has the structure of a mortal, but his wizened skin consists of leaves and bark, with a blanket of branches layering his back – a great yew tree morphed into man, brought to life with astonishing presence through a blend of animatronics and performance capture. He says he was summoned to give guidance to Conor, which he proceeds to do by telling tales of his own past. In the boy’s eyes, however, this arrival holds far greater significance.

Throughout, DP Oscar Faura frames Conor alone in the shot, perpetually isolating him from those around him. Aged just 12, life should solely be made of simple pleasures, but his reality is one of savage complexity. In contrast to the rich, rainbow colours of the drawings he distracts himself with, Conor’s world is stained with sombre greys, overcast clouds, and the oblique tones of Fernando Velázquez’s sorrowful score. At school, he suffers in silence at the hands of the playground bully (James Melville), his mind constantly consumed by the trauma of his terminally ill mother (Felicity Jones).

As the Monster himself describes, Conor’s story is one of a boy “too old to be a kid, yet too young to be a man”, an age-old trope, but one that has rarely been tackled with such confronting honesty. Eschewing sentimentalism entirely, director J.A. Bayona, working from American author Patrick Ness’ adaptation of his own novel, approaches the material with a plangency that’s more The Orphanage than The Impossible – not so much tugging at the heartstrings, as wrenching at them.A Monster CallsA Monster Calls demonstrates the sort of authoritative filmmaking that children’s cinema so often seems determined to avoid. Lewis MacDougall may only be a young teen, but his performance is spurred by an emotional depth way beyond his years. “Everyone wants to talk” Conor says despondently as his mother’s health continues to deteriorate, but the fact is no one – not his disappointing father (Toby Kebbell), nor his domineering grandmother (Sigourney Weaver) – wants to listen, and through that void his vulnerability manifests in shattering silence.

Crucially, the film never mawkishly exploits its subject matter, and instead opts for tactful sincerity that evokes memories of Guillermo del Toro’s Pan’s Labyrinth and Gábor Csupó’s Bridge to Terabithia. The stories Conor sees in his imagination, brought to life through a beautiful blend of watercolour paint and CG animation, are a therapy for him; a gateway to help process his grief.

Ness’ title may be a literal reference to Neeson’s Ent, but the real monster here is the illness. We watch through the eyes of a boy, but we see the anguish of all those who surround him: Jones and Weaver’s drained, undying despair resonant of the personal devastation faced by anyone beset by the loss of someone they couldn’t bear to live without. So much more than just a children’s story, this is a mature and mournful masterpiece.

★★★★★