Most dance plays make me wish that the cast would shut up or keep still. That's not the case with David Pownall's "The Edge" -- a tense, haunting work being performed through Sunday by Britain's The Kosh group at the Theatre Project in Baltimore.

The reason "Edge" is good theater is simple: The two principal media, dance and declamation, aren't mixed. Words are a compulsive urge for Hanna, the mother in this two-character play. She's a worrier who keeps reraking yesterday's ashes and poking into the chips for tomorrow's blaze. Her daughter lives for the moment; her every nerve is open to time present, and to keep moving is an expressive necessity. Hanna, acted by Mary Ellen Ray, talks a rapid stream for the play's uninterrupted full hour. The daughter, portrayed by Sian Williams, wouldn't get a word in edgewise even if she were a talker, so she responds in the language of movement and dance.

We meet Hanna first. She's a tired hiker, having arrived at a cliff top on a Mediterranean island. Afraid of the edge, she plops down safely at stage center and begins her long complaint. The more she talks, the more she reveals about herself, her daughter and a third character -- the husband and father. Though he never appears, he becomes as real and, ultimately, as enigmatic as the two people we see.

From Hanna's initial remarks about her daughter one forms a concrete image, and the young woman's actual appearance is a surprise. She is a free spirit, almost a fairy-tale sprite. Without contradicting anything we've learned, her behavior lends another dimension to the family situation. As she scampers dangerously along the cliff's edge, taunts her mother and shyly, impulsively engages in the give-and-take of anger and love, the play opens up the possibilities of an additional interpretation -- less materialistic, more mythic -- of blood ties.

Pownall is a wonderful wordsmith. His language ranges from the casual to the poetic, yet it is always at the service of storytelling. The choreography, by Johnny Hutch in collaboration with Williams herself, is fresh and also serves the somewhat different story it conveys. If the dance isn't constantly inventive after the first 40 minutes, it certainly is never boring.

Under Michael Merwitzer's direction, Ray and Williams perform with nonstop virtuosity. Ray's acting establishes the appearances of the real world and the mother's middle-class, middle-aged practicality while subliminally asking the audience how a woman becomes this way. Williams makes one fall in love with her and at the same time makes one fear such rashness. Yvonne Swindon's costumes and Howard J. Davidson's postimpressionist music contribute to the characterizations and the magic of a bright Mediterranean afternoon, but wouldn't a devastatingly blue cyclorama have been more apt than Jenny Carey's black-and-white backdrop of curtains and balloons?