In the preface to his novel Therese Raquin, Emile Zola states his intention of demonstrating the 'total absence of the soul'. His story of a sanguine man's affair with an unhappily married woman, the Frenchman writes, is a 'scientific' study of the clash of human temperaments, with the aim of seeking the animal in human characters that are 'devoid of free will'.

If only Park Chan-wook had heeded those words when he used Zola's story as the basis for his vampire drama, Thirst. Park's film starts as a poised piece about religion and redemption, but soon spins out of control through a mix of awkward melodrama and goofy comedy.

Thirst begins brightly as the protagonist is introduced. Gentle, dutiful priest Sang-hyun (Song Kang-ho, above right) is a tortured soul, his benign appearance belying his struggle to comprehend the workings of a cruel world. His confusion is compounded by his dual role as spiritual mentor and hospital worker, prescribing both prayers and pills to his parishioners-cum-patients.

As his melancholy slowly segues into depression, he makes a move akin to suicide: he volunteers to head to Africa to take part in an experiment seeking a vaccine for a deadly disease.

He dies, but is revived when injected with a mysterious batch of blood - one that not only gives him life but also superhuman powers and a craving for blood. His perplexity grows as he has to contend with a growing band of miracle-seeking followers and a transgressive desire that begins with blood and ends with sex.

The latter soon becomes available when he meets Tae-ju (Kim Ok-vin, above left), the wife of his childhood friend Kang-woo (Shin Ka-hyun). Just as in Therese Raquin, an affair soon ensues, one with fatal consequences as Tae-ju coaxes Sang-hyun into killing Kang-woo, claiming he and his mother (Kim Hae-sook) had been abusing her for years.

It's here that Park ups the blood-splattering ante, as the now murderous pair - with Tae-ju soon joining Sang-hyun as one of the undead - let their desires run amok, their initial affection soon descending into confrontation and farce because of their divergent personalities. Sadly it's also at this point that Thirst becomes farcical.

While Song and Kim deliver engaging performances as a self-loathing man and a vengeful vixen, their efforts are eclipsed by increasingly fantastical imagery, with the film finally becoming The War of the Roses played out through cartoonish antics. Such frivolity takes the steam out of the film's tragic finale.

It's a shame Park chose such an awkward stylistic melange for Thirst; the film has a cultivated look with subtle symbols that could have fuelled myriad subtexts: the clash between Sang-hyun's austere habitat and the gauche decor of Kang-woo's house, the interweaving use of Bach's cantatas and Korean pop from the 1940s - all these could have highlighted a clash in cultural and moral values. Sadly, such deft touches are submerged by the visual and narrative hyperactivity in the film's second half.

As with his previous film, the underperforming I'm a Cyborg but That's OK, Park seems out on a limb when he touches on narratives broaching on the supernatural. Maybe it's time he returns to exploring the darker side of humanity through the gritty basics. Zola would probably agree.

Thirst opens today