Traverse Theatre, Edinburgh Neil Cooper ****

There are moments in David Greig's 2002 play when it looks like it might become a treatise on how a ruling elite can co-opt an entire community for their cause. It is true that the two Cambridge naturalists investigating the bird-life on a remote Scottish island prior to the outbreak of World War Two are agents of the state on unwitting reconnaissance. Once the island's dour custodian Kirk is out of the way, however, the nature-watch conducted by the mercurial Robert and his wet-behind-the-ears sidekick John takes on an altogether more liberating tone. This is particularly the case where Kirk's niece Ellen is concerned.

By the second half, the trio are en route to creating a pagan Eden for themselves a million miles from buttoned-up mainland conventions. It is here where things really begin to fly in Richard Baron's up close and personal touring revival for the Borders-based Firebrand company in partnership with Heart of Hawick. One minute Robert and John are doing an accidental slapstick routine with Kirk's body, the next the play's simmering erotic undercurrent has given way to full on sexual awakenings as human nature and animal mentality merge as one.

This is performed with such poetically realised force by James Rottger as John, Martin Richardson as Robert and Helen Mackay as Ellen that it all but becomes an anthropological dance or primal mating ritual, with Ellen's libertine siren spirit leading the charge. It is this desire for purity that makes Greig's play so quietly subversive. Only when Crawford Logan's Captain prepares to take Ellen and John back to a civilisation where war rather than free love looks set to reign does reality finally bite.