TORONTO — There is a breathtaking moment at the end of “Hamnet,” the tear factory that had its Canadian premiere Sunday at the Toronto International Film Festival.

Without robbing you of the startling, rich satisfaction of experiencing it, know that a young mother, played by the transcendent Jessie Buckley, comes to terms with unfathomable loss by extending a gesture that no moviegoer with blood in their veins will be able to shake for a long, long time.

In less capable hands than Oscar-winning “Nomadland” director Chloe Zhao, the scene could have been cheesy, odd or shamelessly sentimental. But the earthy move is none of those things. It’s the profound coda of one of the best movies of the year. 

And one of the most emotionally draining — in a good, cathartic, cheaper-than-therapy way.

That changed mom is Agnes Shakespeare, William’s wife, who’s better known as Ann Hathaway.

And it’s no spoiler to say that their 11-year-old son Hamnet dies. The audience walks in prepared for a tragedy. Well, they think they’re ready. In reality, because of Buckley and Paul Mescal’s passionate and intrusively real portrayal of Agnes and Will’s love soothing us into submission, we’re shellshocked when it finally arrives.

The going gets tough, but there are many rewards to reap from these parents’ agonizing journey. “Hamnet,” based on Maggie O’Farrell’s novel, uses the Bard and his bride to explore grief and the healing potential of art, and asks how the little boy’s death might have impacted “Hamlet,” arguably the greatest play ever written.

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While Shakespeare is a historical figure that little concrete information is known about, it’s safe to say that “to be or not to be,” “the slings and arrows of outrageous fortune” and “he is dead and gone, lady” were probably not lines written by a grinning author.

O’Farrell and Zhao, back and better than ever after Marvel’s eternal “Eternals,” take that sapling of an idea and let it grow.

The crying valve isn’t opened right away, though. “Hamnet” begins intoxicatingly romantic as it imagines Will’s early, lusty courting of Agnes when they lived in rural England, which is postcard pretty here; more ancient, supernatural Forest of Arden than Kiera Knightley staring off at rolling green hills. Spitfire Agnes is an aspiring wood sprite who spends all her time under the trees making concoctions out of herbs.

Nobody wants her — except Shakespeare. Could do worse.

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They marry, have three kids and then Will moves to London to support the tight-knit family. It’s a recognizable domestic crossroads, and the script doesn’t overburden the plot with a bunch of “a-ha!” Easter eggs relating to his plays like “Shakespeare In Love” did. In fact, I only heard his full name spoken once. Instead, “Hamnet” aims to be a relatable, albeit lush and sweeping, “what if I were in their shoes?” drama.

At first, ideally matched Mescal and Buckley smolder. As they age — and the tale jumps forward abruptly — they connect beautifully with the child actors who play their kids, especially the precocious Jacobi Jupe as poor Hamnet. 

Jacobi’s big brother, Noah Jupe, by the way, takes on the role of the Danish prince on opening night of “Hamlet” at the Globe. The clever way Zhao takes advantage of the siblings’ resemblance is shattering.

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So is Mescal. For the entire film, it’s a relief to see the Irish actor get to speak above a breathy whisper. He tends to play shy loners with gym memberships — in “Normal People,” “Aftersun” and somehow even wielding a sword in “Gladiator 2″ — and the bashfulness suits him. This time he’s more extroverted and full of life. Funnily enough, a playwright is his most commanding role so far. 

When he hugs his wife — hard — as their lives take a turn, it’s the kind of unsparing raw spontaneity that most films run away from in terror.

However, it’s Buckley who’s giving one of those rare turns that simply beggars belief. She swings back and forth from cast iron to porcelain. The actress is thunderous, playful, grounded and ethereal. She breaks your heart — not only when the worst befalls Agnes, but whenever she cracks a smile.

I’ve adored her in movies and onstage for years. She’s mostly been part of outre projects such as “I’m Thinking of Ending Things” and “Women Talking.” “Hamnet,” despite the difficult subject matter, is one of her most mainstream and hopefully most watched films so far. 

If you’re not yet familiar with her work, get thee to a cinema.