365, Edinburgh Playhouse, Edinburgh

"In theatre, people are desperate for stories. So what happens when a character comes on stage who does not have one, or does not know it, or does not want to tell it? What does that mean for an audience?" asks the director Vicky Featherstone. It means, in 365, that the audience is as lost and unengaged as these 14 characters in search of a play.

A new collaboration from the National Theatre of Scotland, the company that created Black Watch, and David Harrower, writer of the tense two-hander Blackbird, was one of the most eagerly anticipated events at Edinburgh this year. In the event, 365 felt so much like a work in progress that it might have been wiser if the International Festival director Jonathan Mills had pulled it, or rebranded it as a "workshop" performance.

What inspired Harrower was the launch each year of some 6,000 children in care into the community, with only a transitional spell in a "practice flat" to learn how to manage life. On a set made up of various living arrangements – a collage by designer Georgia McGuinness of parts of interior and exterior living quarters – a group of care-leavers is trying to grasp their future by grabbing what they can of their fragmented past.

Featherstone and Harrower have drawn on exhaustive research, with input from their plucky young cast, to create a patchwork of stories, strait-jacketed into a sprawling dramatic form. Memories are excavated, nightmares relived, social disorders accentuated and insecurities preyed upon, while stilted instructions from a "practice" life manual are inserted in voiceover.

A gawky youth, keen to become a chef, struggles with a toaster; a teenager abandoned as a child forces her mother to explain her callousness, two brothers encounter each other in angry confrontation; a disturbed teenage mother signals for help by setting fire to her practice flat; two girls struggle to escape the tyranny of an abusive boy. No wonder the social worker seems a little harassed.

The actors are not always audible and, in spite of some concentrated acting, you never believe you are watching a play with much emotional texture. Yet 365 has potential, and its subject matter is worth developing beyond what is little more than a "practice play".

Transferring to Lyric Hammersmith, London W6 (0871 221 1722), 8 to 27 September