While the Hollywood assembly line cranks out more and more formulaic, cookie-cutter psycho movies about slashers, stalkers and serial killers, a hit French thriller has slipped in under the radar, so sublimely subtle and tangible it makes "The Talented Mr. Ripley" look like a dog and pony show.

The film is called "With a Friend Like Harry" and the title character has an M.O. similar to Tom Ripley's -- he elbows his way into the life of an old classmate who doesn't remember him. But Harry (Sergi Lopez) certainly remembers -- scratch that -- has memorized everything about Michel (Laurent Lucas), a man he hasn't seen in 20 years.

The two of them meet by chance in a service station bathroom as Michel and his family are on their way to their fixer-upper country cottage for a vacation. By way of offering Michel's kids and wife a ride in his air-conditioned Mercedes on this stiflingly hot day, Harry invites himself and his sumptuous young fiancée Plum (Sophie Guillemin, "L'ennui") along on this family vacation.

Harry is charming and carefree enough that Michel and Claire (Mathilde Seigner) ignore those little internal voices that tell them something is creepy about this guy -- like the fact that he can recite by heart a poem Michel wrote in high school and had long since forgotten himself.

Yikes.

As the viewer, you know with certainty there's something not quite right with Harry -- after all, it's practically says so in the title. But thanks mostly to a spectacularly -- but not conspicuously -- elusive performance by Lopez ("An Affair of Love") you just can't quite put your finger on it. What, you keep thinking, is this guy's angle?

Co-writer and director Dominik Moll keeps you off-balance throughout the movie, sprinkling in a healthy dose of humor as Michel shows faint signs of envy. I mean, let's face it: Harry is idly rich, free of responsibility and has a blindly devoted, adorably sexy girlfriend. But Michel's feelings are never overt. Moll is such a crafty director that such things are just understood through stealthy incidental indicators, like the simple shot of Harry's Mercedes in the rear view mirror of Michel's fatigued station wagon. You don't even see his face yet you know exactly what Michel is thinking.

So does Harry, apparently. In a disquietingly generous gesture, he insists on buying Michel and Claire a brand new SUV. He also continues to stay with them (how can they insist he leave now?), as his intrusions grow more jarring and personal. He tells old school stories just this side of creepy ("Remember Anna? I dated her after you did."). He asks invasive questions ("Isn't it time your told your parents to get out of your life?"). He pushes Michel to resume his "writing career" with puzzling insistence. And all the while he smiles an innocuously blank but strangely unsettling smile that will make the hairs on the back of your neck stand up.

Moll's exquisite mastery of the film's strong symbolism and abstruse ambiance makes "Harry" at once very amusing and wildly uncomfortable. Like a resourceful chef, he adds a pinch of tension here and a dollop of disturbing behavior there, until Harry's twisted psyche begins to emerge as he secretly and systematically begins sabotaging or eliminating anything (and anyone) he sees as an obstacle to Michel's triumphant return to the literary arts.

Why? You'd have to ask Harry. But the fact that you still can't figure out this now full-blown sociopath is exactly what keeps you on pins and needles all the way to the closing credits.

I think I can say safely and with unabashed delight that I've never seen a movie as shrewdly chilling as this one.