PATRICIA Highsmith’s novel “The Price of Salt” provides writer Phyllis Nagy with the foundation for director Todd Haynes’s unhurried examination of a love affair between an older upper-class woman and a young immigrant shopgirl.

Carol’s (Cate Blanchett) marriage with Harge (Kyle Chandler) is on the way to dissolution. For Christmas 1955, Carol sees a model train that she wants to give to their small daughter. The salesgirl is Therese (Rooney Mara). Carol leaves her gloves on the counter. Therese arranges to return them. So begins an odyssey that follows converging paths into dangerous territory in an era when love between two women was anathema among America’s wealthy.

Carol has no plan for after her marriage ends. Therese is interested in photography as an art, a hobby and perhaps a profession. Their relationship develops at a leisurely, even lethargic, pace. After Harge’s lawyers tell Carol’s lawyers that Harge demands sole custody of the child, Carol decides to spend Christmas alone. She invites Therese to accompany her. The film unfolds during a gentle automotive passacaglia westward in Carol’s magnificent Packard sedan. Friendship develops during nights in motels, first in separate rooms, then in separate beds in one room, ultlmately in the same bed making a tentative physical exploration of love.

The film is a low-intensity tour de force for Cate Blanchett as a woman in whom social style mingles with strong independence, sharing with Rooney Mara a memorable denouement so subtle as to easily miss if you blink.

At Palace Electric, Capitol 6, Dendy