If you were to find yourself in the unfortunate position of speaking with Sy Parrish, you’d wish for the conversation to end immediately. It wouldn’t so much be the topic of discussion; there is an innocent lilt to his occasionally invasive questions.

No, it’s his sadness and loneliness, and the unsettling feeling that no matter how nice anyone really is to Sy, those emotions will rule his life. And while his thinning hair and pudgy midsection don’t cut a menacing figure, he brings a quiet aggression to the simplest of acts, such as tousling a child’s hair. It seems only a matter of time before he turns the volume up, and you probably don’t want to be around.

Of all people, Robin Williams portrays this character in One Hour Photo. His performance is a precise, haunting balance of menace and pathos. As we’re disturbed by Sy’s actions, we also sympathize with him. In the past, Williams has only been able to both frighten and elicit sympathy from us when we look at his spotty cinema resume. All the hype for One Hour Photo has been based around his performance, and it’s a chillingly real deal.

Sy works at the Sav-Mart photo development counter, where he knows everyone in the neighborhood and the idiosyncrasies of their photographic lives. But no family attracts his attention more than the Yorkins. Will Yorkin (Michael Vartan) owns his own design company, wife Nina (Connie Nielsen) has the dream home she has longed for, and they have a son, Jakob (Dylan Smith), who even at 9 years old shows compassion for the feelings of others.

For nearly a decade, Sy has developed the Yorkins’ photos and has grown enamored with their seemingly storybook life. He feels so close to the family that he envisions himself being welcomed into their home, treated as “Uncle Sy.” But his utopian fantasies are shattered when he learns about Will’s infidelities. What upsets him even more is that the family structure seems oblivious to this problem. And the only way he can correct that is to turn his sadness into madness.

Writer / director Mark Romanek is yet another transplant director, this film representing his leap from videos on MTV to the big screen. Fortunately, like David Fincher and Spike Jonze before him, Romanek ensures his visual flair contributes to the narrative, not just flashy images. The world of One Hour Photo is at times unbearably cold and sterile, much the same way Sy must see it. There are fantasy sequences that are both frightening and telling about Sy’s fears. And Romanek makes exceptional use of space to symbolize how isolated Sy is. The best such segment is when Sy, seeking comfort, finds it in the bedroom furniture display at the Sav-Mart – he feels more at home in a staged domestic setting than in his real life.

As a director, Romanek makes some excellent choices and has a future worth watching out for. But his screenwriting falls into some logic traps that are hard to swallow in a movie that otherwise seems plausible. For instance, it seems unlikely that Sy would have access to Sav-Mart’s weapons case in the first place, let alone at the specific time he opens it. And, unless he wanted to be caught – a potential nuance Romanek doesn’t tackle – Will would not be seen hopping into his mistress’ convertible right outside the front door of his office.

Without these plot points, though, the third act could not be set in motion, and watching Williams’ full realization of his character during this act overshadows the story problems. Even when acting out the most disturbing movements in his plan, Sy has a childlike expression of whimsy on his face. It’s as thought getting caught might be part of the anticipation. And in the final scene, Williams delivers a shattering closing speech that cuts right to the heart of Sy’s character.

There has been much to-do about Williams’ so-called “bad guy trilogy” in 2002 – the other two performances being Insomnia and Death to Smoochy. Williams was good in the former as a smug villain foil and, like all else in the latter, fell prey to the rampant unpleasantness. Here, Sy’s terrible acts are fueled by the natural desire to connect with others that we all share – that human element drives Williams in this, the best and boldest performance of his career.