Some shows write themselves instantly in the history books, and not always for good reasons. The latest entry into the field of the cataclysmic is Behind the Iron Mask - you might well wish that you were wearing a blindfold if not a full mask (not to mention earplugs) while watching the catastrophe unfold.

The musical hall of shame - stretching from fiascos like Carrie (adapted from the Stephen King novel about a menstruating teenager into a notorious RSC flop-eretta) to The Fields of Ambrosia (where "everyone knows ya"), Out of the Blue (set in the aftermath of the Nagasaki-H bomb and redubbed 'A Flash in Japan' after its short-lived 16-day run) and last year’s Oscar Wilde (opened and closed on the same night) - now has serious competition in the notoriety stakes. With Behind the Iron Mask, the theatrical equivalent of rubber-neckers (people who gawp at car crashes) can be treated to a musical that isn't so much wrecked and bleeding as simply stillborn. It seldom rouses itself into anything resembling life.

At the start, we meet a 17th-century French prisoner (masked throughout, for reasons never explained), who immediately sings "Why am I here?/I can't move/There's no escape/I'm here forever." The dread fear filled my heart that I would soon enough know exactly how he feels. This is a musical about imprisonment that duly (and dully) imprisons its audience for two hours (though at least some had the opportunity to flee in the interval, and many did).

This is one of those phantom exercises in attempting to create a new musical clearly inspired by The Phantom of the Opera, but it should never have left the drawing board. It exchanges one man in a mask for another, with a parallel story of a gypsy woman drawn unwittingly into his lair and into his heart.

None of this, however, is properly motivated; it just happens. Ditto the strange marshalling of proceedings that a jailer has to fulfil. It's all set to a gloppy, synthetic (and heavily synthesised) score, with music and lyrics by John Robinson (except for two songs that are set to words by Lords Tennyson and Byron).

Tony Craven's grim-looking production - on Nicolai Hart Hansen's unbelievably cheap-looking set - fails to harness much energy, though all three actors are to be commended for their apparent sincerity in the face of such adversity. In particular, Robert Fardell's prisoner - his face hidden by the iron mask that makes him look like a cross between a grey Halloween pumpkin, Shrek and Hannibal Lecter - manages to dredge up some strong vocal tones from the depths of the contraption he’s buried within. Mark McKerracher's jailer also desperately tries to rise above the drek, while Sheila Ferguson's Gypsy, sounding like a vamped-up Shirley Bassey at times, acts hopelessly but at 57 still looks ravishing.

- Mark Shenton