There's this little concept in theater known as "Act III." In a performance, in a play or a film, it's usually the concluding act, the complete picture, the end game, the grand finale.

Take the familiar three-act plot structure of: Boy meets girl, boy loses girl, boy gets girl. (Think "Notting Hill," "Slumdog Millionaire," "It Happened One Night" or pretty much every romantic comedy ever made.) Without Act III, we're stuck with a poor forlorn boy, standing out in the rain, alone and unloved. What happens next? Without Act III, we don't know.

So we excitedly await Act III to play out, to let us know how everything we've witnessed thus far turns out.

Keep this in mind for later.

In Alex Proyas' brutally realistic "Knowing," a time capsule has been ceremonially unearthed at an elementary school after 50 years underground. Children in 1959 filled the tube with their crayoned assumptions of what life would be like in far distant 2009—space ships and robots, the iPod (oh, not really) and modern marvels galore.

Nicolas Cage plays astrophysicist John Koestler, an MIT professor and doting father. His wife died a year ago, and John's still coming to terms with her loss. Is there significance to our lives or are we all just swimming around a giant vat of meaninglessness, awaiting inevitable tragedy?

John is present (coincidence or fate?) at the elementary school when the time capsule is opened. His son Caleb (Chandler Canterbury) is the recipient of one of the children's drawings, made 50 years before. Yet while all Caleb's classmates receive pretty pictures, Caleb gets a page filled with hundreds of random numbers. Just so happens, we flash back 50 years and discover that a somber, creepy little girl named Lucinda is the perpetrator of this strange algorithm.

John is intrigued with his son's gift and begins to decipher the code. Turns out the page is a symbolic reference to all the major catastrophes of the last 50 years: for example, he deduces the sequence 911012859 represents 9/11/01, 2,859 people killed. The page is filled with such accurate predictions.

And so, "Knowing" begins to play out as an astute, intense psychological thriller. Not only does John seem to be tracking fate, but fate is tracking him; he is present at the code's next two prophecies, an airplane crash and a subway accident, both incidents portrayed on screen with a disturbing, heartpounding visual alacrity.

The next catastrophe? John's stunned to realize it's a big one, beyond comprehension . . . the ciphering seems to predict the end of the world. And it's right around the corner.

Until this time, we've been following John in a gripping existential mystery. Caleb is haunted by terrifying nightmares, visited by creatures that also tormented poor Lucinda 50 years before.

But then a strange thing happens. Act II closes with a deafening roar of suspected dread and mounting terror, and Act III opens . . . as something else entirely. Something altogether different, as if we've veered abruptly out of psychothriller land to find ourselves standing at the corner of SciFi Street and Biblical Reference Boulevard. Questions, questions . . . suddenly I have all these questions!

Until now we've not been sure if John's insane, or if Caleb's psychic, or quite where this ghostly, goosebumprending psychological drama is headed. But here?

I don't wish to imply that it's a bad ending—just unexpected in a gear-grinding sort of way. And I suppose there's no small way to play out director Alex Proyas' vision of our future. (We love "Dr. Strangelove," don't we?) Still, I can't but feel I've been whumped over the head by a startling Louisville Slugger of a finale that I can't quite come to terms with.

Sure, some might find "Knowing's" final act compelling. Prophetic. Profound. "Knowing" is simply one of those films you'll either love or hate, period. And you certainly won't forget it very quickly. Just that occasionally, over the top really is over the top . . . too much of a good thing being, sometimes, just too much. I suspect this is "Knowing's" fate.