I am still thinking about what made Clouds of Sils Maria such an unusual film. That's how I know it's worth seeing.

It is possible to outline the plot and have it sound like a conventional story. But the way the story is told is strange, and that oddness is subtle.

Maria (Juliette Binoche) is an actress made famous by her role as Sigrid, both on stage and on screen in Wilhelm Melchior's play Maloja's Snake. She and her personal assistant Valentine (Kristen Stewart) are travelling to Zurich to accept an award for Melchior when they receive news of his death. Maria is emotional but the evening unfolds as planned. She is courted by a famed director who wants to restage Maloja's Snake with Maria in the role of the older women who she once seduced and controlled as the young Sigrid.

The second section takes place in Sils Maria, Wilhelm's home in the Alps, where his widow has invited Val and Maria to stay. Maria has accepted the role but rages against its indignity. She and Val drink, talk, hike, rehearse. Their days are deceptively leisurely as is the pace of the film. I had no idea where the story was going. She meets her young costar, a Lohan-esque out-of-control talent. Val champions the brave acting of the young actress after watching her latest blockbuster superhero movie but Maria can't take it seriously at all.

Finally, Maria is in London as the play opens. Val is gone and we never know how or why. End of story.

The centre of the film is the relationship between Maria and Val. Stewart is absolutely mesmerizing and so natural in the role. She is almost more of a manager than an assistant, giving advice and pushing Maria into the more daring roles she thinks she should take. She is the defender of pop culture and new ideas. In the final scene, Maria considers taking an offer to play a genetic hybrid for a young hotshot director - just the type of role Val imagined for her.

Given that Maloja's Snake is about an affair between an older woman and her assistant, it is impossible not to read a layer of desire into Maria and Val's relationship. But there are hints only. They are friends and work colleagues who spend a lot of time alone together so the way they heavily fill each others' lives is very believable. The dialogue and dynamic between the two is fascinating and totally different from almost any similar filmic relationship that I can recall.

Perhaps the main weakness of the film is that Maloja's Snake is such a tedious and badly-written play. It seems obvious and without much psychological depth. Given that we watch many of its scenes being rehearsed, I wish it had more substance.

As much as I enjoyed Something in the Air, Olivier Assayas's previous film (VIFF 2012), Clouds of Sils Maria was so much more engrossing and stayed with me far longer.