How dreary is the weather in Cornwall? Well, Mike Shepherd, artistic director of Kneehigh, a theater based there, said he was looking forward to being in Minneapolis this week. That's how dreary it is. Constant rain has flooded towns on the jutting southwestern peninsula of Great Britain. When the clouds break, winds of 30 miles per hour have kicked up, according to BBC news.

"I have my thermal underwear all set," Shepherd said, when warned about Minnesota's unusually cold winter. He knows what he's getting into. Kneehigh brought "Brief Encounter" to the Guthrie Theater in February 2010. The company this time brings "Tristan & Yseult," a tale more deeply embedded in its Cornish roots. It opens Friday on the proscenium stage.

Kneehigh spent 10 weeks in California last year, at Berkeley Rep, which certainly would have been more hospitable, weather-wise.

Kneehigh is considered one of the great cultural treasures of Cornwall, which is historic as one of the six Celtic nations — territories where Celtic language and tradition have survived.

"Cornwall is our physical and spiritual home," states the company's Web page. "We draw inspiration from the landscapes, history, people and culture."

"Tristan & Yseult" has become the company's best-known work. In a 2013 review, the Guardian newspaper said the production established Kneehigh as the "de facto National Theatre of Cornwall."

Kneehigh first built "Tristan & Yseult" in 2004. It is based on the ancient legend of a Cornish prince and Irish princess who fall into a bewitched and adulterous love affair. There are, as Shepherd puts it, "happier and sadder versions" of the story, but ultimately this type of star-crossed romance always ends badly for the lovers. Jealous spouses in this case hold the key. Still, Shepherd said, there is room for compassion, forgiveness and understanding.

Director Emma Rice, who also directed "Brief Encounter," assembled the show and brought it back last summer after eight years.

Shepherd cautioned not to take the tragic love story (which would influence Shakespeare's "Romeo and Juliet") too seriously. When Kneehigh first created the piece, the company was "into Tarantino," Shepherd said. So that influence is there, and Rice also threaded the Wagner opera ("Tristan und Isolde") through the piece. There are gargoyles, trainspotters and other manner of oddball characters.

"It is a celebration of theatricality," Shepherd said. Costuming, for example, is determined by the personality of the character, not a specific era. Music and dance are eclectic and jump around, but the chronological jumping-off point is somewhere in the 1950s. "Whatever the story demands," Shepherd said of the universe in which the story exists.

This aesthetic — archly theatrical, full of invention and eagerly open to moments of sheer performance — infused "Brief Encounter." In that case, some critics (this one included) felt that the craziness bruised a gentle Noël Coward story of futile and forbidden love.

" 'Brief Encounter' was different," Shepherd said. "It was moved to the West End and had a sophistication of production values. 'Tristan' is still a wildly inventive celebration. I wouldn't say it's less sophisticated, but it's bolder and epic — played in high winds."

Much like the well-soaked earth, the crashing surf and the rugged seacoast of Cornwall.