A RUTH Rendell mystery. A Bill Kenwright tour. A Classic Thriller Theatre Company show. A cast with Robert Duncan, Sophie Ward, Chris Ellison, Ben Nealon, Shirley Anne Field, Deborah Grant and Blue's Antony Costa in the ranks, directed by Roy Marsden.

Well, it certainly sounded promising and the Grand Opera House has had a good track record for thrillers, Gaslight especially lingering in the memory from early this year.

Adapted for the stage by the highly experienced Simon Brett and Antony Lampard, Rendell's psychological drama is set in 1978, although that wasn't obvious from the indecisive clothing, but apparently cassette recorders were all the rage and there was nothing more exciting for the posh family to do on the master's birthday than watch Don Giovanni on the telly, when surely such a family would have travelled somewhere exotic overseas to attend a night at the opera.

The storyline starts with the crime scene established already at Lowfield Hall, police blue tape barring the door to where all the Coverdales have been shot in a Valentine's Day massacre.

Steady-eddie Detective Superintendent Vetch (a solid Chris Ellison) has come up from London to lead local lad Detective Sergeant Challoner (2017-bearded Ben Nealon) in their enquiries, which begin with eccentric spinster housekeeper Eunice Parchman (Sophie Ward), who has chosen to stay on after the bloodshed, thereby raising suspicions as much as Ward's strange wig.

Guided by the inspectors' thorough, measured plod of an investigation, Rendell's story takes us back to the start of her employment and so gradually to the fateful night. Opera-loving George Coverdale (Robert Duncan) runs a business, letting his jolly second wife Jacqueline (Rosie Thomson) run the house as well as a little art gallery and some charity events (all very familiar to the North Yorkshire high society, no doubt!).

His daughter Melinda (Pamela Dwyer) and her son Giles (Joshua Price) call each other "step" and seem out of step with the world around them; she's flighty, fidgety, with her heart and mind on her boyfriend elsewhere; melancholic teenager Giles is fixated on death and alternative lifestyles.

There is already a tactless, taciturn housekeeper out of sorts, Eva Baalham (Shirley Anne Field), floating around mournfully; ne'er-do-well petty crook Rodger Meadows (Antony Costa, as Blue turns green) is the family's cocky new gardener working his parole, still with a thing for Melinda. He waltzes into the hall at will; so too does raucous post mistress Joan Smith (Deborah Grant) in gaudy Bet Lynch garb, quoting great chunks of the Bible, seemingly with a bit of previous with George.

Excruciatingly loud in every way, she is a wholly unbelievable character, typical of the uneven, pot-holed tone of a bizarre play where the humour, grey rather than black, is uncertain; the sudden bursts of violence over the top; the simplistic class divide ludicrously exaggerated and frankly patronising to one and all.

Erratic as they may be, Marsden's cast don't stand a chance; the play's dark secret is no such thing; perhaps we should send for Miss Marple, in residence at the Theatre Royal this week, to solve the mystery of whytheydunitatall.

A Judgement In Stone, The Classic Thriller Company, Grand Opera House, York, until Saturday. Box office: 0844 871 3024 or at atgtickets.com/york