HE makes his way silently through the auditorium, appearing from the darkness to take centre stage.

It's a fitting entrance for the mysterious figure at the heart of An Inspector Calls, JB Priestley's powerful comment on social injustice.

Actor Liam Brennan, who plays the enigmatic Inspector Goole, sits hidden among the audience before making his entrance.

"I sit at the back of the stalls and watch the opening scene," says Liam. "I prefer to do that rather than just walking straight in. The inspector comes from the people; it makes sense for him to come out of the audience.

"The opening is very stirring, accompanied to music that sounds like it's from a Hitchcock movie."

Stephen Daldry’s innovative staging of the play brings the story of the Birling family into the 21st century. Though still a period piece, set in the early 1900s, its themes of capitalism, class and human compassion continue to resonate. What do any of the Birlings have to do with a young woman called Eva Smith, whose downward spiral leads to despair and suicide? Very little, they would have us believe, but the inspector has his own theories.

"I'd never seen An Inspector Calls on stage, I'd only seen the old film and last year's BBC production (partly filmed in Saltaire)," says Liam. "My thinking behind the inspector is that he's normally completely in control, he knows it will all go his way, but I didn't want to play him with too much complacency. My inspector knows there is a time limit, he's always looking at his watch."

The relevance of time doesn't come clear until the end. The family is left unsettled, and onlookers who have been quietly present throughout the performance gather together, creating the sense of community that Priestley called for in society.

"The inspector's big speech at the end, about how we're all responsible for each other, leaves an impression on the audience," says Liam. "Because it's a school text we get lots of young audiences in, some are a bit rowdy but they seem to be enjoying it. It's great that live theatre can engage young audiences like that.

"For many of them, it may be the first time they have been to the theatre. Hopefully, if we've done the job right, they will want to come back and see something else."

The set is dominated by the Birlings' family home, lit up like a giant dolls house and balancing precariously above a dirty street. When the house opens up, the family literally look down on their visitor, who stands in the street grilling each of them in turn.

"Goole teases them out of their ivory tower, they come down a spiral staircase into the street. It's a great set but a little dangerous - there are cobbles, an iron staircase, and the house is on stilts. You have to watch where you're going!"" says Perth actor Liam, who theatre work includes extensive Shakespeare productions. He has also performed Shakespeare on the radio, his TV credits include Shetland and Taggart, and he won the 2006 CATS Award for Best Actor for his performance in Tales From Hollywood at Perth Theatre.

Most of the non-speaking roles are taken by local actors, including children who are the first to appear on stage in the opening scene. "They only had Tuesday morning to rehearse, before the opening night. They've done really well," says Liam.

There is something special about watching the play in the city where JB Priestley is from. "When I get a spare hour I'll have a wander and visit the Priestley statue," says Liam. "I'd like to pay my respect."

* An Inspector Calls runs at the Alhambra until tomorrow. For tickets call (01274) 432000.