It is no surprise that children, to whom so much is yet unknown, are often afraid of the dark and all the mysteries it hides in the shadows beneath the bed or behind closet doors. But Conor O’Malley, the young protagonist of J. A. Bayona’s “A Monster Calls,” is 12, old enough to have opened the closet door, looked under the bed and devoured scary monster movies like “Godzilla.”

So in the gloom of 12:07 a.m., when an ancient yew rips itself from the ground behind his Irish home with the nightmare sound of 100 haunted-house doors splitting apart, Conor’s only response is a vaguely annoyed scowl.

Switching tactics, the towering fire-eyed beast makes Conor an unexpected deal: He will tell the boy three true stories, then Conor (Lewis MacDougall) will tell him the true and shameful story of the real fears the boy dares not speak, the ones he, his stern grandmother (Sigourney Weaver), and his dying mother (Felicity Jones) keep avoiding.

In most kids’ films, the monster is a fantastical threat roused from the darkest, deepest depths. In Mr. Bayona’s tough-minded film about grief, the monster’s purpose is to shine a light on a child’s most real and rational fears. On the level of both story and narrative form, “A Monster Calls” confronts a universal adult dilemma: how much should adults, whether family or filmmakers, soften hard truths for children?