J.A. Bayona’s adaptation of Patrick Ness‘ A Monster Calls must be one of the most well-received world premieres of this year’s Toronto Film Festival. The movie is a heartbreaking and truly moving grief parable for kids, about a young boy named Conor, whose mother is in the final weeks of an unsuccessful battle with cancer. As nightly visits by a giant monster fail to traumatize a boy already going through the worst of traumas, the monster tells Conor a series of stories that question the fairy tale understanding of heroes and villains, right and wrong.

Stopping by our Toronto studio with his cast and author-screenwriter Ness, J.A. Bayona told me his first read-through of the book was overwhelming. “I was surprised by the number of ideas it had in common with my other films,” he noted of the film that is nevertheless incredibly distinct in style and execution from The Impossible and The Orphanage. “The movie gave me the chance to explore storytelling and try to shed some light on the ultimate meaning of what I do as a filmmaker.”

Ness adapted his own book and refused to sell the rights until he met the right filmmaker. “I could see all these things Bayona and the actors brought to it that I would never have thought of in a million years,” he said.

Sigourney Weaver, who plays Conor’s strict but loving grandmother in A Monster Calls, praised the script read-through Bayona built into the schedule. “Liam [Neeson] was there reading the monster,” she noted. “It was wonderful to hear it read out loud, and it gave you a lovely feeling of starting together. People don’t do read-throughs very much anymore, and I think they’re awfully valuable for everybody.”

Agreed Felicity Jones, who plays Conor’s dying mother: “[They’re] so important. It takes away some of the nerves as well when everyone’s in the room together. If you never have that moment, everyone’s working a little bit more disparate. It’s great to come together and understand the tone of the film you’re in.”

Bayona told me newcomer Lewis MacDougall, who appeared in Pan, was the obvious front-runner from the field of boys auditioned. The young actor said his audition culminated in a screen test in Barcelona. “There were three or four other boys auditioning for Conor,” MacDougall noted. “That was the first time I really reached the emotions I would do later in the film.”

The depth and sorrow of those emotions led to wails of tears from the audience at the Roy Thomson Hall earlier in the week, as the magical film unspooled. A Monster Calls gets a limited release in December ahead of a wide rollout in January. Check out more from the cast and crew in our exclusive video above.

Videos produced by Neil Hansen/Route Eleven, camera work by Meaghan Gable and Ida Jokinen. Special thanks to Image Skin Care CanadaCalii LoveCommune, Dan Gunam, and Silverline Studios.