Love means always having to say you're sorry in this lachrymose supernatural romance. It's unfamiliar territory for Johnnie To Kei-fung, devoid of the stylised violence and black humour that have made him one of Hong Kong's most distinctive filmmakers.

Which is not to say that Linger doesn't have its moments. The script, by Ivy Ho (who wrote Comrades, Almost a Love Story), displays moments of insight into the troubled psyche of paralegal Yan (Li Bingbing; right), a disturbed young woman who has yet to recover emotionally from a traffic accident three years earlier.

The lead-up to this incident is related in a five-minute pre-title sequence, set on a college campus so sappily rhapsodic that it could pass for the Hong Kong branch of Jay Chou's academy in last year's Secret. That is, until a lover's spat between Yan and campus hot shot Dong (Vic Chou Yu-min, right) results in the latter's death and mercifully propels the narrative into a darker direction.

Although she recovers physically, Yan is so wracked by guilt that she increasingly shuns all company other than that of Dong's wandering spirit. A central question for Yan - and the viewer - is whether he is a figment of her imagination or a ghost seeking closure before going on to the next world. It's a familiar theme in both Hong Kong and Hollywood cinema, and Linger in this respect offers little that is fresh or intriguing.

Some of the most effective sequences delineate Yan's struggle to separate fantasy from reality as her behaviour accelerates into self-destructiveness. There are also some surprisingly tender moments involving Dong's surly father (Yau Yung) which, as blatantly manipulative as they may be, are performed with a sincerity that's hard to resist. The film is on less solid ground when it comes to ersatz poetic touches such as the flying butterflies of the film's Chinese title and their symbolism of departed spirits finally able to shuffle off this mortal coil.

A big problem in Linger is the total lack of chemistry between Yan and Dong. It's an inauspicious big-screen debut for F4 band member Chou, who radiates so little charisma it's a wonder Yan pursued him in the first place. More convincing is the attraction between Yan and the ne'er-do-well (Wong Yau-nam) her law firm is defending, a forbidden lust that generates more heat than the leads.

Although there's little to mark the film as a To production, the director's fans will enjoy seeing his regulars playing characters far removed from their typical roles, including the usually loutish Lam Suet as Yan's middle-class father, tough guy Roy Cheung Yiu-yeung as a psychiatrist and Maggie Shiu Mei-kei as a butch lawyer.

Linger is screening now