126 minutes/Opens tomorrow/ *****
The story: In the Los Angeles of an unspecified future, Theodore Twombly (Joaquin Phoenix) ghost-writes personal letters for a living. Insular and broken-hearted from an impending divorce from his wife Catherine (Rooney Mara), he installs an intelligent operating system which calls herself Samantha (the voice of Scarlett Johansson).
This is that rare thing, a film of sci-fi ideas that suffuses its futurescapes with real emotion - found here are gentle humour and joy, but most of all, an aching melancholy.
Much of the profound sense of loss and longing that suffuses this work from writer-director Spike Jonze comes from the sound, set and costume design.
Jonze (Where The Wild Things Are, 2009; Adaptation, 2002) uses music from art-indie sources such as Arcade Fire and Karen O to stunning effect.
This is a future with a retro feel, where organic pianos and guitars are the soundtrack behind the activities of men in high-waisted wool pants and women in fuzzy sweaters and where everyone opts for warm summer shades of peach and rust.
Jonze could easily have made everything look and feel grey, steely and industrial.
Given the film's themes, that would have been the obvious and easiest artistic choice, but he is too smart to hit things squarely on their heads.
Twombly's world is our world, of course, but with better technology, enabling people to touch one another in ways that are paradoxically ever more distancing. This is not a new idea in speculative fiction, of course.
Omnipresent smart devices allow Twombly, as they do everyone else, to retreat deeper into his interior even as his physical self exists within the guts of a megacity.
Each citizen, to some degree, is an otaku, a digital shut-in, preferring the easy intimacy of man-machine interaction to the messy, contradictory and ill-defined nature of real human interaction.
Twombly treats a date (Olivia Wilde) like an emotional automated teller machine - he takes what he needs and no more, a pattern he might have adopted with soon-to-be former wife Catherine (Mara).
With neighbour and close friend Amy (Amy Adams), he has a deep bond, but it is one complicated by their ties to their artificial soulmates.
Phoenix, as the maudlin introvert whose confidence and happiness grow as he falls deeper in love with a voice in his earpiece, gives the performance of his career.
Johansson's reading of Samantha - warm and sultry at first, then wiser and more distant as her mind evolves - is faultless.
The love story that plays out between human and abstract intelligence - the soul of the machine - develops romantically between Twombly and Samantha, and platonically between Amy and her computer.
Their ties to machine avatars, entities with bottomless reserves of sympathy, are never shown to be creepy or dehumanising. Rather, Jonze says the opposite is true. That line of thinking gives this work the power to move, and most of all, to surprise.