GREAT job, this. Saturday afternoon I'm watching Big Bird prance around the Edinburgh Playhouse stage in Sesame Street Live. Saturday evening I'm up to my thighs in water, wading through the middle of a river towards the so-called Devil's Pulpit in Finnich Glen.

In an act bordering on hubris, the NVA Organisation is going head-to-head with nature, attempting to turn a place of stunning physical beauty into a scene of comparably stunning art. Dishing out waders and army helmets, Angus Farquhar's company - Scotland's only true theatrical innovator - leads a nightly band of 75 people through the high waters, past animals both stuffed and alarmingly alive, to a makeshift platform in the heart of the gorge, while shadowy figures, lit by open fires, peer down from the precipices.

Woodland rambles were never like this in my day. But is it just the townies larking about in the great outdoors, the Internet kids on a low-tech field trip to gild an already breath-taking lily? Don't you believe it. For at least the third time in my life, Farquhar and his cohorts have created a moment of sublime theatrical brilliance, not competing with nature but taking her on side, enhancing and animating the landscape with a sound-and-light show at turns seductive and heart-stoppingly alarming.

It peaks with a spectacular fountain spray of water, a burning mannequin, and a swooping hawk. There is no applause. The gorge is gorgeous. And no post-show audience I've been in was ever so subdued.

The Secret Sign ends on Saturday. It is a matter of national urgency that the sell-out run be extended.