"The Secret in Their Eyes" was an obscure surprise when it won the Oscar for best foreign film this year, beating such formidable entries as "The White Ribbon" and "A Prophet."

Now comes the real revelation. This Argentine detective story is one hell of a great movie. Expertly written, played and directed, it's the best romantic mystery since "L.A. Confidential."

Set in 1999 and 1974, partly a cold-case police thriller and partly a smart, sentimental grown-up romance, this could have been a movie divided against itself. Following twin stories of obsessive love, it's so ambitious it shouldn't work.

Yet all the characters carry us along and the intricate plot structure fits together. The one-two punch at the finale — a shock climax that pins viewers to their seats and a satisfying sentimental ending — leaves you elated.

The film's hero is Benjamin, a retired judicial investigator (played by Ricardo Darin, a shrewd, romantic Alan Rickman type). For 25 years he has been haunted by an unresolved rape-murder case.

Not unsolved; the culprit wriggled away through a crack in Argentina's old, corrupt political power structure. Benjamin hopes to exorcise his obsession by writing a novel about the investigation; one of the film's themes is the way memories can inspire some people and entrap others. Returning to his old office in Buenos Aires, he reconnects with Irene (Soledad Villamil), the lovely, whip-smart prosecutor on the killing, now a judge with a husband and family. They talk over the case, but they're really tiptoeing around the fact that they nearly became lovers a generation ago.

The film makes us clue-gathering detectives as it time-travels, patiently filling in the larger narrative via brief flashbacks.

In 1974, Benjamin and his wry, alcoholic colleague, Pablo (Guillermo Francella), take on the case of a small-town beauty murdered shortly after she married and moved to the city.

Following hunches and clues, the pair exonerate her heartbroken widower, Pablo (Ricardo Morales), and winnow down the universe of suspects.

Director Juan Jose Campanella stages a breathtaking five-minute sequence that gives us a visual equivalent for their efforts. It begins high above a crowded stadium, swoops down to crowd level and becomes a fast, exciting chase.

Campanella also shows us the intellectual and emotional excitement of cracking a case. In a scene between Darin and Villamil, her character intuitively realizes how to work with him to break a suspect. Campanella gives their telepathic teamwork the snap and sizzle of a thrilling dance routine.

But within the network of corruption and illegality in the police and the government, justice is elusive — official justice, that is; creative people will always find a way.

The film oscillates between suspenseful recollections of the bad old days and bright hopes for the future, never losing emotional contact with the audience. It gives us breathers and laughs, but the tension never goes flat. The almost-lovers deliver marvelously sensual performances, and the personalities of the secondary heroes and villains are fully sketched in. It's rare for a film to be thought-provoking and outlandishly entertaining at the same time. This time the Oscar voters nailed it.