Rock climbing, as Emm (Rachael Joffred) discovers in Nice People Theatre Company's world premiere of Grace, or the Art of Climbing at the Power Plant in Old City, requires the united efforts of every muscle fiber and neuron. It's a taut, focused sport, the endorphin rush of ascent matched by the constant threat of a plunge, instinct working with strategy, raw internal fortitude paired, indeed, with external grace.

It's also a pretty handy metaphor if you're writing, as Lauren Feldman is, about a young woman struggling to climb out of a crushing depression. Emm has every reason to remain at the boulder's base: a bad breakup, job loss, sick father. But Feldman's writing never allows Emm to wallow; she's sad enough to skip a week's worth of showers, self-aware enough to joke about it. She keeps climbing, first pegs in her father's garage, then the footholds at a local rock gym. With each step, she finds a higher ledge to cling to, and to help pull herself out of her crevasse.

The ensemble is strong, with nimble performances by Bi Jean Ngo, Bob Weick, Armando Batista, Kevin Meehan, Mary Tuomanen, and Dan Hodge. But Joffred anchors - or rather, belays - the piece with a vulnerability that is reflected in her saucer eyes and slouched shoulders. When Emm's friends (all conjured by her imagination - she's too fragile to return their real-life phone calls) talk about solids not really being solid but just clusters of cells huddled together, they might be discussing her own too-permeable skin. All of 25, she says wistfully, "There was a time when whatever trouble I caused, I was worth it."

Emm wants to know what she's supposed to do with all the useless intimacies she's collected - scent and taste memories, the feel of a lover's earlobe between her teeth - once a relationship ends. Feldman's answer is to keep moving; the burden may never lift, but movement can make it feel lighter. For Emm, movement, ever upward, is a gift.

Feldman's script isn't as tight or muscular as it might be, considering that it uses physical exertion as a framework. It is, however, ably assisted by Pirronne Yousefzadeh's direction, teamed with Caitlin Lainoff's rugged 360-degree rock-gym set and Mike Inwood's lighting, which guides the audience's attention around the warehouse space. This show might be less captivating without the set's versatility and the climbers' constant kinesis, and even with all that, there's too much rumination and self-analysis.

Still, the play, like its heroine, has a lot of heart and gets where it's going (one of many "Rule number ones" of climbing: Always know where you're going) one deliberate step at a time.