The Nero Conspiracy by Enzo Condello, directed by Beng Oh. Designed by Kat Chishkovsky, lighting by Nick Merrylees, sound by Robert Harewood. With Ian Rooney, Giovanni Bartuccio, Leon Durr, Tani Lentini, Simon Kearney, Steven Cabral, Christopher Broadstock, Josie Scott, Steven Dawson and Lauren Clare. Old Council Chambers, Trades Hall, Carlton, until April 2.

I'm not sure whether The Nero Conspiracy isn't one of the most naive plays I have ever seen. It's as if Enzo Condello simply decided that he wanted to write a Shakespearean tragedy and then went ahead and did it - blank verse, ornate language and all - blithely unaware of all the reasons why such a project might be impossible in the early 21st century.

I don't mean "naive" in any pejorative sense; indeed, a certain naivety, even stupidity, has always seemed to me an important ingredient of art, although it must be balanced by a concomitant sophistication. As Heiner Muller said: "Stupidity is a prerequisite for poets. I am a good example of this... Maybe I have too little fear."

And in fact, one thing that is striking about both this play and its production is its fearlessness. Director Beng Oh, whose work is new to me, meets the challenges of Condello's text head on, and in the process creates a powerful contemporary example of tragic theatre. It may be raw; it may even be, on reflection, something that oughtn't to work at all: but it seems to me that The Nero Conspiracy misses being a triumph by only the narrowest of margins.

The play retells Tacitus's history of a plot by members of Rome's aristocracy to assassinate the corrupt and tryannical Roman emperor Nero. Condello - drawing on Seneca's bloody tragedies, which influenced the Jacobeans as well as Shakespeare - creates a fast-moving and gripping drama. It has to be said that when Condello reaches for Shakespearean metaphorical complexities his language most often falters, falling into mere pastiche: he lacks the linguistic and dramatic finesse of his models. But for the most part, the play is written in muscular, plain blank verse, and it's surprisingly effective and economical.

What makes the play is, I think, Condello's solid sense of dramatic structure, which permits the inexorable unfolding of events to exert its own fatal fascination. Certainly, despite a feeling that the text was sometimes overwritten - especially at the end, where the powerful climax and denouement are muffled by the inclusion of three or four minutes of unnecessary dialogue - I was never bored.

Beng Oh's production is exemplary, attaining moments of authentic grandeur and horrible beauty. His sense of orchestration occasionally falters - it is a fine line he is treading here - but for the most part his direction is sure and compelling. He uses the simplest of resources to create a visual language drenched in the dark sensual splendour of Renaissance painting, highlighted by the operatic music which largely constitutes the sound. The wonderful opening scene, in which each character enters one by one and sits at a table draped with a white cloth, is for example clearly based on Da Vinci's The Last Supper.

But the major visual inspiration for the design is the dramatic painting of human form by Caravaggio, and here the lighting and design are crucial. The most important element is a plain red curtain that can be drawn across the middle of the stage, and many scenes are played against its vivid folds. The set is very simple: props are ordinary household objects, costumes neutrally contemporary, suggesting rather than illustrating the milieu of Ancient Rome. Nick Merrylees' expressive lighting enacts a lush chiaroscuro across the human forms on stage and makes the most of Kat Chishkovsky's design, which exploits the classic Victorian architecture of the Old Council Chamber space to its full.

But this would be mere framing if it were not for the high quality of the performances, which almost without exception meet the complex emotional and technical demands of this play. The scenes enacting human brutality are among the most effective I have seen in a theatre. This is, after all, a theatre of cruelty: Seneca's tragedies gave birth to Shakespeare's sadistic tragedy Titus Andronicus and the blood-drenched extremities of Jacobean drama, and Beng Oh picks up this tradition with an almost ascetic directness: it is the restraint which makes these scenes so potent.

The rape of the slave woman Epicharus (Tania Lentini) by Nero (Giovanni Bartuccio) early in the play is only surpassed by her torture, which is almost unwatchable. Violence of this extremity is very difficult to do well on stage: it is too easy for it to slip into the grotesquely comic. Here it is unambiguously horrifying, as if you were watching the real thing. This effect is not due to any particular gore on stage: it results from the ingenious manipulation of an audience's imaginative capacity, and some totally committed acting.

But tragedy is of course about pity as much as terror, and there is plenty of that as the characters in this tragedy struggle with events which they are powerless to resist or control as Rome's political climate darkens into slaughter. The final scenes between Seneca (Ian Rooney) and his wife Paulina (Josie Scott) manage to reach an extremity of pathos which is genuinely moving. And Seneca's suicide, the climax of the play, is at once sombre, grand and desolate.

Theatre of this imaginative ambition is rare anywhere, and it's worth seeing The Nero Conspiracy for that alone. I can't help feeling that this is at once one of the most peculiar and most arresting plays I will see this year. And I will watch Beng Oh's future development with enormous interest.

Bookings: Trades Hall, 9513 9363