An eleven-year-old boy – thin, tired-looking, young for his age – is fixing himself some breakfast. There's something in the preoccupied way he sorts this out that shows he is practised at it; no minute is left unused; he's putting the washing on while waiting for the toast to pop. He's not tutting or shouting up to his parents to ask where the detergent is. As his grandmother points out, 'no boy should wipe down a surface without being asked first'.

The reason for this quiet household efficiency is that the boy, Conor (played with subtlety and conviction by Lewis MacDougall) is losing his mother to cancer. Felicity Jones brings a sweet sturdiness to the role of his mum which is well-judged in its displays of emotion; she never overshadows MacDougall, but we well know how much it pains her to know she is leaving him. Conor's father is long out of active parenthood, as well as out of the country – he flies in from LA for a quick, and perhaps slightly damaging visit, despite his matiness with Conor. Between a father who doesn't have space in his new American flat for his older child, a grandmother (Sigourney Weaver, who is all clipped efficiency if slightly wobbly transatlantic vowels) who can't really suffer children in her neat home, and a bunch of bullies at school, it's becoming clear that Conor needs someone to help him through.

That friend comes in the least likely – and really quite unfriendly-seeming – package: an anthropomorphic yew tree, voiced with aplomb by Liam Neeson. The Monster appears by night, telling stories of murder and belief, and attempts to shake Conor from his burgeoning rage. The effects are spellbinding – energy fizzles up through the roots of this gigantic tree-beast.

It's slightly hard to judge the audience for this 12A-rated film; it's certainly too sad for young children. At several points, mid-sob, I knew I'd have to inhale and was worried about making a swamp-like snort from the back row (I wasn't the only one). The dialogue is a little clunky, at times, but mostly it's beautifully pitched, and MacDougall and Jones between them make this a rending, changing experience of a film.

How can we deal with a huge, unshakeable grief? How is anger best mastered? A Monster Calls doesn't provide direct answers, but more oblique ones which are more universally relevant, and ultimately of more use.