Dana Reitz dances during a rehearsal of "Necessary Weather" at the American Dance Institute on March 23. (Tracy A. Woodward/THE WASHINGTON POST)

At one point in “Necessary Weather,” dancers Dana Reitz and Sara Rudner break from their more mysterious permutations to launch into a brief novelty act. They hum “Tea for Two” and pad barefoot through a jaunty little soft-shoe number.

It’s a whimsical nod to the fact that their entire hour-long duet, which they performed Saturday and Sunday at the American Dance Institute in Rockville, is itself a novelty act, though not in the way you’d expect. The gimmicks, if you could call them that, were serious matters of art. Maybe too serious.

What struck me first was the self-importance of the work, which the two women have been performing on and off for several years. As the audience filed into the black-box space, we were warned not to step on the special covering of the stage floor. To make sure we obeyed, a row of attendants stood guard at the floor’s edge.

If they seemed like overkill, their presence set up an atmosphere of reverence (and remoteness) that continued in the performance. Wearing loose white tunics and trousers, Reitz and Rudner stood out against the darkness like high priestesses of purity. They danced in contemplative silence.

The air of Japanese-tea-ceremony solemnity felt like a throwback to postmodern dance of the 1960s and ’70s, where a certain aloofness toward the audience reigned. Indeed, that’s the environment in which Reitz, primarily a solo artist and choreographer, and Rudner, a dancer with Twyla Tharp in her early years, forged their dance careers.

Both women are now in their 60s. You might say their ages are one of the gimmicks in “Necessary Weather,” and it’s also a point of admiration. Throughout the hour, they hardly stopped moving, and they never lost the luxurious melt and fluidity in their shoulders, arms and hips. Especially in Rudner’s case:The softness of her joints and bright, engaging way she used her eyes reminded me of the similar charms possessed by Indian classical dancers.

Another novelty is the work’s sole design element: Jennifer Tipton’s lighting, so mutable and expressive as to be a third performer. Tipton, who in a career spanning a half-century has worked with many of the top-ranking choreographers and companies, is the queen of dance-lighting designers. Her name on a work’s creative team is an instant signifier of taste and quality. So it was here: all the drama and much of the emotion in “Necessary Weather” sifted into the space through her palette of shadow and brightness.

A few spectacular, lightning-strike moments punctuated the piece, which unspooled at an otherwise slow, even pace, like a tai chi practice. In one, a spotlight caught Rudner like the beam of an alien spaceship. As the light hit her, Rudner arched backward as if electrified, and we saw a current of energy course up one arm, shiver along her shoulders and wriggle through her fingertips. Her mop of graying corkscrew curls gleamed like polished silver. Ever so slowly, through a subtle softening in her spine and neck, it grew clear that Rudner had surrendered to the light and luxuriated in its heat.

Reitz had her own moment of sun worship, though in keeping with her more minimal, inner-directed movement style, hers was not the full-body release that Rudner showed us. At one point, she lay curled up on the floor, then with a slight, sharp shift of her body she thrust her face into a tiny beam that lit it against the darkness like a mask. Or rather, like the Cheshire Cat, her grin hinting at a secret we’d never crack.

There were many secrets in this work — too many. Long passages of lovely but inscrutable gestures began to feel obsessive. I was grateful for little bits of wit, like the “Tea for Two” soft-shoe fragment and a surprising instance when a straw hat the two women held between them took on a lantern’s glow. Peering into it as if it were a cook fire, Reitz and Rudner began to chat contentedly the way women do, idle murmurings about a grown son and his girlfriend. Ingeniousness merged with domestic routine, and it was delightful.

How I wished for more glimpses of personality, more of a way inside these intriguing performers. After all, that pristine floor was wide open. It looked like a perfect spot for play.