Vermandero, lord of the castle of Alicante, has engaged his daughter Beatrice-Joanna to a young nobleman, Alonso de Piraquo, but she falls in love with Alsemero, another young man. Alsemero suggests he kill Alonso, but Beatrice entrusts the job to De Flores, a disfigured servant who adores her but whom she loathes. Meanwhile, two of Vermandero's followers, Antonio and Franciscus, disguise themselves as madmen to gain access to Isabella, wife of the jealous Alibius, owner of the local madhouse. De Flores murders Alonso, hides the body and demands his reward from Beatrice: her virginity. Repelled but trapped, she submits. Alsemero is betrothed to Beatrice, but Alonso's brother Tomazo suspects foul play. Antonio and Franciscus secretly declare their passion to Isabella. She pretends to go along with them, playing them off against each other.

Beatrice, perversely drawn to De Flores, continues her affair with him. To keep her deflowering a secret, she bribes her maid Diaphanta to take her place in the bridal bed. Diaphanta willingly complies, after which De Flores kills her to ensure her silence. Denounced by Isabella, Antonio and Franciscus are brought by Alibius to the castle where Vermandero, at Tomazo's urging, accuses them of Alonso's murder. Alsemero, grown suspicious, questions Beatrice who admits everything. He locks her up, but she escapes, pursued by De Flores. The pair stab each other fatally, and make their dying confessions to Vermandero and his household.

As a play, The Changeling is a mess. A typically gory Jacobean drama of murder and illicit passion by Thomas Middleton, it is tenuously yoked to a knock about subplot reckoned to be the work of Middleton's collaborator William Rowley. Not that the main plot is without its crudities, both verbal and dramatic - Middleton was certainly no Shakespeare - but at its heart (which has ensured the play's survival on-stage) is the twisted relationship between Beatrice and De Flores, in which she becomes sexually obsessed with a man she finds mentally and physically loathsome.

Some stage productions, embarrassed by Rowley's subplot, try cutting it out entirely. First time feature director Marcus Thompson, as writer-director of the first-ever screen adaptation, has no such inhibitions, not only taking on board both playwrights' contributions but tossing in a good deal of his own. (As a title, Middleton's Changeling is altogether too modest.) Much of the original text is cut, and a lot of what remains is brusquely updated. There's certainly no cause to be reverential towards Middleton's verse (let alone Rowley's cloddish prose), so when Alsemero's friend Jasperino, played by black actor Leo Wringer, greets Beatrice with a cheery, "Yo, sister!" it scarcely jars. The same can't be said, though, for Beatrice's line to De Flores: "You're wasting my fucking time."

Unlike Baz Luhrmann's invigorating assault on Romeo and Juliet, Middleton's Changeling isn't a whole-hearted update. More after the fashion of Derek Jarman's The Tempest or Caravaggio, the film sports willful anachronisms: characters in ruffs and doublets ride around in black stretch limos, and bemused package tourists swell the crowd of wedding guests. But Thompson lacks both Luhrmann's style and Jarman's polemic; in place of any thought-through approach to the material, there's a readiness to stir in whatever comes to hand. Performance poet John Cooper Clarke pops up to deliver his trademark monotonous rants, and the madhouse scenes (involving much writhing, howling and smoke canisters) look like out-takes from Ken Russell's The Devils (1971).

To be fair, some of this unevenness can be ascribed to the saga behind the production, which makes Welles's Othello (1952) sound like an easy shoot. This film was seven years in the making, during which time some of the cast died before they could be filmed (Fernando Rey), others before they could be voiced (Vivian Stanshall, a sadly silent presence), and the rights to the original music track were abruptly withdrawn. Under the circumstances, it's perhaps remarkable that anything works. But Thompson's insistence on using the craggy fortress of Alicante (the original's setting) as location yields dividends. Some of the imagery is powerful (and rather more plain crass), and Jacobean audiences would have reveled in seeing De Flores (Ian Dury, with the worst case of cinematic acne since Freddy Krueger) vigorously humping Beatrice on top of the trunk containing her butchered fiance. Amanda Ray-King's inadequacy as Beatrice, though, takes much of the steam out of the central coupling, and several of the cast seem to be acting in some other movie altogether.

Middleton's Changeling is frequently amateurish and clumsy, and it goes ludicrously wrong far more often than it goes right, but there's a raw, anything-goes energy and an irrepressible enthusiasm about it that, in a paradoxical way, is faithful to the spirit of the original. Even without knowing anything of the tortuous production history, this unmistakably comes across as a film that somebody passionately wanted to make. At least those who dismiss British literary-adaptation cinema as bloodlessly tame and tasteful can be assured that this, for once, is nothing of the sort.

TEX PENTHOLLOW