Six Characters In Search Of An Author, Royal Lyceum Theatre, Edinburgh

Luigi Pirandello's seminal Six Characters in Search of an Author, premiered in Rome in 1921, is the archetypal tough nut. Philosophising broadly on the nature of existence and identity, the work has been so influential that the now rather postmodern offspring it has spawned leave the original in danger of looking dated.

Here, David Harrower's excellent free-ranging 2000 adaptation is given a freshening up by the Knives in Hens author. As pithy as ever, well-intentioned if rather stilted, it plays out the core shocking events with a powerful intensity.

The premise of Six Characters... is simple enough: in a rehearsal room, assorted actors, stage managers and a director rehearse a Pirandello play until they are interrupted by six people who claim they are abandoned characters from an author's pen, looking for a stage on which to tell their story. Mark Thomson's production is set firmly in its 1920s milieu, the six – clad in dumpy mourning clothes – announcing their presence from a box in the auditorium, a seminal moment that doesn't here have enough impact to suggest that these characters are different.

As they try to cajole and bully the director into giving them a chance to act out their "story", it becomes clear that characters without a plot are destined to bash out the same unresolved scenario for eternity. The interest is in how these living two-dimensional characters seem rather more three-dimensional than the stereotypes who make up the "actors" and stage hands around them. Indeed, we get the feeling that what we actually have is six characters in need of a therapy session – and what more postmodern thought could an audience have?

There's some nice ensemble playing. Amy Manson as the overwrought Stepdaughter holds the production together, her laugh a maniacal drone. John Dougall as the Director struts around somewhat wearily, bleakly aware, one senses, that he is doomed to be one of life's watchers.

But the production cannot shake off a rather leaden atmosphere. All the world may be a stage, but these players need a more contemporary kick to fully implicate this audience.

To 8 March (0131-248 4848), transferring to the Citizens Theatre, Glasgow (0141-429 0022), 12 to 29 March