If the Bridewell is the cutting edge of London's new musical scene, then The Ballad of Little Jo is the sharpest knife in the drawer. This American musical is raw, dramatic and highly absorbing, and its European premiere sits perfectly in the intimate surroundings of this gem of a theatre, sadly under threat of closure.

In 1860s Boston, wealthy young Josephine Monaghan has a child out of wedlock and flees west to escape her responsibilities and the disapproval of her family. In Idaho, en route to California, she's brutally raped, and after cutting her hair and scarring herself, decides to pass herself off as a man for protection. So begins her troubled double life in a rural mining community.

Anna Francolini - whose voice is gentle and strong but without being overpowering - plays Jo with great feeling, and assumes her macho disguise by investing it with a real, necessary edge.

As her friends, a young couple who struggle with their own feelings for Jo, Kieran Brown and Karen Evans are both brilliant. Their public and private faces as man and wife alter tellingly as they negotiate the fragile nature of their relationship, particularly in their number "Do You Love Me?", in which both shine. Amongst a role-juggling, 14-strong ensemble, Ellen O'Grady stands out, bringing to commanding life three very different frontier women.

The writing talent of Mike Reid and Sarah Schlesinger is evident throughout. Where others might resort to predictable rhyming couplets, these two have created a musical that's a brilliantly balanced and always engaging mix of dialogue and music as diverse as ballads, ragtime tunes and American working ditties.

And, in Carol Metcalfe's Bridewell production, the rest of the creative team rise to the challenge of staging a show of the highest quality, no matter space or budgetary restraints. Martin Robinson's costumes are periodically accurate, Kate Bannister and Karl Swinyard's wooded set flexible enough to support many different locations and Hansjorg Schmidt's lighting ideally atmospheric. (Though, at times, the constant fog of dry ice is a little distracting.)

The Ballad of Little Jo has a key issue at its heart - identity. The characters long for a sense of belonging and acceptance, battling social expectations and prejudices relating to class, gender and race as well. The beautiful "Listen to the Rain", sung in an absorbing performance by Phong Truong, is a reflection of one immigrant's otherwise hidden personality.

This is what musical theatre should aspire to be. Don't miss out.

- Jake Brunger