Focus Features has unveiled a new behind-the-scenes featurette for A Monster Calls, which details the project’s inception going all the way back to the origins of the Patrick Ness book. As Ness explains in the video, the story for A Monster Calls actually originated from author Siobhan Dowd, who began working on the book but unfortunately died of cancer before she could dig into the novel in earnest. Ness picked up Dowd’s original idea and wrote the fantasy novel that exists today, and that serves as the basis for the feature film from director J.A. Bayona (The Impossible).

Ness actually wrote the script for A Monster Calls as well, and the film stars Lewis MacDougall as a 12-year-old-boy who is having trouble coming to terms with his mother’s illness. Felicity Jones plays the mother, a woman in the final stages of chemotherapy, and in order to cope (or avoid coping) with the ordeal, MacDougall’s character is visited by a giant tree from the neighboring graveyard who proceeds to tell the boy three stories.

The stories within the story are animated gorgeously within the context of the film, and while some people took issue with the manipulative nature of the picture, I found it moving and earnest enough to looks past some minor qualms. It’s absolutely a film worth seeing, but it’s also one of the most devastating tearjerkers in recent memory. Bring tissues.

Check out the new featurette below, click here to read my full review, and click here for Aubrey's interview with Ness. A Monster Calls opens in theaters on December 23rd.