The distinctively complicated relationship between a celebrity and personal assistant coincides with an aging actress' realization that she can no longer play the ingénue in "Clouds of Sils Maria," an understated character drama from writer-director Olivier Assayas (2009's resplendent "Summer Hours"). Over twenty years ago, Maria Enders (Juliette Binoche) launched her career with the star-making role of Sigrid in master playwright-filmmaker Wilhelm Melchior's play (and later film), "Maloja Snake." En route to Zurich with dedicated assistant Valentine (Kristen Stewart) to accept a lifetime achievement award on Melchior's behalf, Maria learns that he has died suddenly of a heart attack. His body is barely cold yet when she is approached by respected director Klaus Diesterweg (Lars Eidinger) to star in a London production of a "Maloja Snake" sequel, with Hollywood starlet Jo-Ann Ellis (Chloë Grace Moretz) set to take over Sigrid and Maria now in the role of the manipulated, middle-aged Helena. Feeling a protectiveness to Sigrid and seeing too many parallels for comfort between herself and Helena, Maria is unsure if she is emotionally capable of taking on a part that hits so close to home.

There have not been many films that get to the heart of the unique rapport between a celeb and their assistant, and it is the unusual dichotomy between Maria and Valentine which "Clouds of Sils Maria" observantly tackles. Regularly juggling two electronic devices at a time as she handles Maria's affairs, Valentine works hard to compensate for a job she knows she was underqualified to get. Employee, consultant, and a friend on the payroll—Valentine must be all of these things and is happy to fulfill said requirements until she starts feeling used and less than appreciated. They may spend a lot of time together—usually with Valentine acting as Maria's sounding board to all her insecurities—but their relationship is still business even when it's personal. This isn't entirely Maria's fault, either, but simply the way it is when one person is working for another.

Juliette Binoche (2014's "Words and Pictures") and Kristen Stewart (2014's "Still Alice") portray Maria and Valentine with an intimate understanding of who these people are, embodying them fully and wholeheartedly. Binoche avoids turning Maria into a caricature or a tyrannical diva; she is relatively down-to-earth for a famous person, but overcome with doubts not only about the stage role of Helena, but about the turning point in her career and life which this fictional character symbolizes. Maria is still receiving project offers, but she is at the point where the younger parts she once went for no longer seem like the right fit. She doesn't want to look like a fool, but also fears becoming marginalized in a profession that so heavily values youth.

Stewart, who became the first American to win the César Award (the French equivalent of the Oscars) for her work here, imbues her role with an emotional freedom and vitality that belies the frustration Valentine begins to experience from the thanklessness of her job. As confident as Stewart comes across, the role's developmental limitations sometimes mimics Valentine's work as a personal assistant. She is there to service Maria, and when she gives her opinion it isn't usually listened to. As the troubled but talented up-and-coming superstar cast as Sigrid, Chloë Grace Moretz (2014's "If I Stay") is tremendously self-assured, cozying up to Maria and showering her with praise when they initially meet before the tides shift and they start to replicate the power struggles of their stage personas.

"Clouds of Sils Maria" gets its name from the snake-like pattern the clouds take as they drift through the mountainside of the Swiss Alps' Engadin valley, a phenomenon both gorgeous and, true to its reptilian appearance, vaguely threatening. Maria's struggle to find her place within the cutthroat business she has found herself never gets easier, but it does evolve as she finds herself aging out of certain parts and having to carve out a new niche. The film, splendidly shot by cinematographer Yorick Le Saux (2014's "Only Lovers Left Alive"), is low-key almost to a fault, a slice-of-life that may not be our own, but certainly strikes an authentic note. As reserved as the script is, however, it threatens to become monotone and repetitious, with one too many scenes of Maria running lines with Valentine as their real-life relationship blurs with the one in the script they are rehearsing. The story, nonchalant even at its most eventful, grows all the more fascinating as the conclusion draws near and Maria has no choice but to come to terms with a career than has given her so much but left her without a single substantial lasting relationship. In regard to "Clouds of Sils Maria," greatness appears to be just out of its grasp. This is a thoughtful, even provocative work, but it lacks that extra dramatic push needed to affect on a deeper level. Instead, one watches at a politely admiring, oddly removed distance. The film, exquisitely performed by Binoche, Stewart and Moretz, remains chilly in spite of its showbiz intimacy, which may be the point all along.