Charlie Kaufman has finally nailed that elusive third act.

The concepts for his mind-expanding screenplays for "Being John Malkovich," "Human Nature," "Confessions of a Dangerous Mind" and "Adaptation" were all audacious and original, but the movies were running on fumes at the end. For Kaufman, the devil was in the details of finding his way out of the cerebral maze in which he isolated his characters.

"Eternal Sunshine of the Spotless Mind" is not only his most accessible and romantic screenplay, it's his most complete. The third act works like a charm and pulls all his themes, characters and conflicts together beautifully.

The film will appeal to Jim Carrey fans and women drawn by Kate Winslet, but there will be a strong core audience of young and older adults who can't wait to see the latest Kaufman brain-tickler. None will be disappointed. Focus Features should enjoy above-average boxoffice for this spotless confection.

The references to the mind and brain in the preceding paragraphs are apt because the movie basically takes place in the mind of Joel Barish (Carrey). Barish knows his relationship with live-in girlfriend Clementine (Winslet) is unraveling, but he gets the shock of his life when he learns that she has had her memory of him completely erased from her mind. Rushing to see the inventor of this process, Dr. Howard Mierzwiak (Tom Wilkinson), he impulsively decides to undergo the procedure too.

After taking a knockout pill at night, Joel falls into a deep sleep while two of Mierzwiak's assistants, Stan (Mark Ruffalo) and Patrick (Elijah Wood), enter his apartment in Yonkers and strap on memory-erasing headgear. Using a map of Clementine's presence in Joel's brain that Dr. Mierzwiak traced the previous day, the brain-scanning device searches and destroys each memory one by one.

The movie now divides into two realities. In one, in Joel's bedroom, Stan and Patrick -- later joined by another office assistant and Stan's girlfriend, Mary (Kirsten Dunst) -- raid Joel's liquor and start to party even as the procedure continues. Patrick's tongue loosens, and he confesses that he fell in love with Clementine while zapping her memories of Joel. Using what he knows about her life and attraction to Joel, Patrick has unethically wormed his way into her bed.

Stan is mildly disconcerted about this but is much more disturbed when his patient begins to resist the procedure and he must call Dr. Mierzwiak for backup.

Which brings us to the second reality -- in Joel's mind. As his memories of Clementine vanish, Joel begins to realize how much he will miss her and what an impact her impetuous nature made on his orderly, over-regulated life. He tries desperately to hide his memory of her in places in his life she never visited. The movie then becomes a race between Joel's frantic efforts to cling to a piece of Clementine and the mad scientists in pursuit of those memories.

Director Michel Gondry, a French music video director who made his directorial debut with Kaufman's "Human Nature," beautifully orchestrates Ellen Kuras' cinematography, Dan Leigh's production design and Valdis Oskarsdottir's editing so memories merge and evaporate seemingly in a single shot. Joel and Clementine move through space as the scenes behind them change and morph like animation cels gone mad.

It's a wonderful concept -- to see a couple relive their life together, going backward, but able to make comments on what each was thinking and to see how each may have misread the other. Most exciting of all is that third act, where characters who no longer know one another must find each other again using the heart and not the mind.

Carrey takes all his usual antic energy and bottles it up tight to portray an anal man both attracted and repelled by Winslet's free spirit who changes her attitudes almost as frequently as her hair color. Wilkinson gives the doctor such a calm intelligence that you almost forget what an appalling device he has invented. Ruffalo is goofy and unthinking, while Wood's puppy love for a former patient has a genuinely nasty side, the equivalent of psychological rape. Dunst is deep into hero worship of all the scientists, especially Wilkinson's gentle guru, without realizing the implications of that hero worship.

For all its science fiction plot, "Eternal Sunshine" is no special-effects extravaganza. The emphasis is always on the characters, their hearts and minds.