SINCE the dozy but delightful days of Bill and Ted, the artist known as Keanu Reeves has replaced the word excellent' for exorcism'.

His taste for the satanic verses was rampant in Dracula and The Devil's Advocate and now he's on the highway to hell again as John Constantine a man on a mission to purge the earth of demons and dodgy angels.

But Constantine is a reluctant hero; he's moody, cynical and has the kind of humility football bosses save for referees.

He's also the kind of guy who treats triumph and disaster as the same. On learning he has lung cancer, he lights up a cigarette and then stubs it out in his own blood. This is a man obviously not too enamoured with life; a kind of semi-martyr on a grisly death row.

Reeves carries off the character of Constantine decently enough, although some may say he's sleepwalking through the role or looks uninterested. That may be true, but most miserabilists do look like they've just got out bed and don't get too excited about life; so that may have been deliberate.

No, the real problem with the film is its lack of fluency in terms of script and plot devices and how these tarnish an otherwise imaginative and intriguing supernatural tale.

The sets are evocative and the special effects stimulating but the story loses it way as the demons gather and, subsequently, we're left with a film of breathtaking vision but hollow execution.

The film opens with a fascinating sequence as Constantine performs an exorcism on a little girl.

But this show of compassion was only carried out because an exorcism was involved and Constantine has no desire to help humans in their day-to-day distress.

Police detective Angela (Rachel Weisz) approaches him for help after her sister commits suicide.

Yet Constantine has no desire to help and wants to carry on ridding the environment of half-breed' angels and demons.

But when these demons seemingly become fully formed, Constantine has to reconsider his position.

Director Francis Lawrence has a background in music videos and it shows as his visual flourishes grace the screen and make for a goth-inspired, eye-catching spectacle.

The action is also short and sharp probably the way our anti-hero wants it but this has an added effect because it refocuses our attentions on the narrative.

And this is where the film heads to hell rather than heaven. The supporting characters are either undeveloped or weak and this drains the menace away from any thrills or shocks that may have been created in the action sequences.

In particular, comedy sidekick Chas (Shia LaBeouf) is a waste and the angel Gabriel, played wonderfully by Tilda Swinton, isn't given enough screen time.

Weisz plays Angela with assurance and conviction but again the character seems a bit muddled and flimsy. But, as in The Matrix trilogy, this is all about Special K. Mr Reeves is back in black and seems to have found a spiritual home as the purveyor and slayer of devils, ghouls and scoundrels.

Constantine is a sporadically entertaining film but lacks the depth and rigour to be regarded as anything other than a mild diversion in the dark arts.

It's bold and brash but ultimately futile. This stairway to heaven isn't all it's cracked up to be.