IF you thought of Robin Williams as a genial funny-man best suited to comedies like Mrs Doubtfire or schmaltzy dramas like Patch Adams, his appearance as a murderer in Insomnia may have gone some way to change that impression.

But his haunting performance as a sociopath tormenting a family in One Hour Photo (15) will have you thinking of him in the same bracket as Anthony Hopkins' Hannibal Lecter.

Mark Romanek makes his feature film debut with this twisted human drama, which showcases Williams's vast talents as a performer.

He plays a loner who will stop at nothing to protect his vision of perfection. His character is a lonely technician who mans the local Sav-Mart one-hour photo booth.

Craving human contact, he develops an obsession with Connie Nielsen's family, inventing fictitious relationships with each family member, especially wife Nielsen and her young son Dylan Smith.

His fixation drives him to make duplicates of their photographs, and even to park outside their house at night and stare longingly at the family he can never have.

When Nielsen's handsome husband Michael Vartan dares to threaten the sanctity of the family unit, Seymour resolves to deal out his own form of punishment.

To say much more would spoil the hairpin twists and turns of the final half hour, which showcase Williams's magnetic screen presence and his fearlessness in tapping into the darker side of human nature.

The actor delivers a sensational performance, which simultaneously inspires fear and sympathy for his lonely stalker.

At heart, all he wants is the security, warmth and love of the family unit. It's just the methods he chooses to achieve his goal which chill the blood.

Nielsen, Vartan and youngster Smith provide sterling support, as does Gary Cole as the Sav-Mart manager who gets on the wrong side of Williams, and pays a sickening price.

Romanek's direction is superb, and he sustains the tension beautifully, cross-cutting between reality and Seymour's fantasy world.

At the end of the day, it's difficult to know which is scarier.