Carol sees Therese too, and they hold each other's gaze for a wistful moment.
But their mutual, immediate attraction isn't that simple.
It's New York City in the early 1950s and same-sex relationships are, at the very least, not a widely accepted public affair.
There's more at stake than just the possible heartbreak of any passionate relationship in this setting.
To complicate matters further, Therese doesn't yet know herself that well, and Carol is navigating a divorce.
Carol's desires are known even to her husband but largely unspoken. Therese is just discovering hers.
It makes the courtship more subtle than most, but this isn't a film about flouting societal norms on some mass scale. It's about these two people and the profound heartbreak of not fitting in the time period that their lives unwittingly occupy.
There is a fascinating contrast in these two women, separated by 16 years in real life. Mara's Therese is a girl-woman, styled, in some cases exceedingly overtly, to look like Audrey Hepburn in the 50s.
This character doesn't have Hepburn's innate elegance and effervescence, though - she is beautiful, but awkward.
When she speaks, she doesn't project so much as swallow her clipped words. She is intelligent, but uncomfortable in and alienated from this world. That otherness is even more evident when she's with her sweet and conventional boyfriend Richard (Jake Lacy).
In striking contrast to Therese, Carol is the epitome of feminine, well-heeled refinement.
Her magnetism and grace inspires obsessions and devotion from those around her - her husband, her devoted more-than-a-friend Abby (Sarah Paulson) - even as she redirects her focus to others.
But it's the love story that's at the centre. Carol remarks that it's as though Therese has been "flung out of space." It could apply to both. Alone, they are lost. Together, they're ablaze.
Few working directors today are able to inventively meld high style and high art in the way that Haynes does.
There are some distracting oddities, including Carrie Brownstein in a very minor role, despite prominent screen credit and Carter Burwell's score, which sounds distinctly like a Philip Glass composed-original, but those are minor quibbles in an otherwise splendidly realised film.
Period movies often can't escape the era in which they're made.
The eyebrows, the makeup, and even the faces all seem to point to another time.
Carol looks like it was actually made in its day - a story transfixes, enchants and reminds us of art's transformative capacity, and we're luckier for it.
Carol
Directed by Todd Haynes
