Every time I saw this movie on my list I had some strange idea in my head it was a romantic comedy of some sort, so I got more intrigued every time I came across the title – both Michelle Williams and Julianne Moore are too discerning (not to mention smart and talented) to appear in studio tosh.

Turns out it's not that at all, but even better, it perfectly suits the incredible talents of two of the greatest female performers alive today.

Williams is Isabel, a young American woman running an orphanage in India with little else in her life but the kids she loves, and she has no time or interest in meeting money people, but if she goes to New York to do so a big payday is promised that will transform her work and let her take care of far more children.

Once there she's installed in a sumptuous hotel suite with her every whim catered to, courtesy of the tech company thinking of making the donation. She's whisked into a lightning fast meeting with the CEO, self-made Theresa (Moore), who insists she likes Isabel and invites her to her daughter's wedding for the weekend of her stay.

Isabel is visibly irritated at having to pander and socialise while her work's waiting for her, but she duly attends. Once there, the story proper kicks in when she locks eyes with Theresa's husband, Oscar (Billy Crudup), and the two are quietly mortified/horrified, some apparently awful history between them.

From there it's impossible not to go without a spoiler warning, because it'd be a very short review - the story teases out the secrets everyone's keeping very slowly and delicately and hinting at great heartbreak. Isabel's first words to Oscar are a venomously bitter 'what did you do?'.

It turns out Theresa's only the adoptive mother of the bride, Grace (Abby Quinn). Isabel and Oscar, once free spirited young lovers, conceived a child, agreed to give it up for adoption and went their separate ways. Instead, Oscar went back to claim Grace and raised her, forging an unshakable bond between them. He married Theresa, who accepted Grace without question as her own child, and they had two more kids, young twin boys.

In a more mawkish film it'd be the set-up for a grand, histrionic melodrama, all slammed doors and declarations of 'you didn't love me, you gave me up.'

But whether it's the script co-written by director Bart Freundlich (along with Susanne Bier, who I'm more familiar with for this kind of thing) or the unassailable delivery of the material from Williams and Moore, it's never less than heartbreakingly realistic.

Theresa has an ulterior motive I won't spoil, which sharpens the emotional conundrum and gives her character even greater depth you doubt any other actress (except maybe Williams) could pull off. When she plays her endgame, it's going to result in impossible choices for everyone.

To call it a tragedy about losing and finding family sounds dreadfully trite – like a hilarious joke it simply can't be described, all you can do is experience it in the hands of masters of the acting craft.