Lenny Haas plays 40-year-old meat packer Henry in 1911 New York City, who dreams of "dancing for royalty" by following in the literal footsteps of ballroom celebrities Vernon and Irene Castle. He rents their old dance studio—a sixth-floor walk-up, $4 a week—and advertises for a partner.

His first and only respondent is Anna (Erin Weaver), who sews beads on garments and overcomes her shyness (and the time's strict proprieties) to dance with Henry every Tuesday evening. They progress slowly (just touching takes weeks), growing from strangers to friends, partners, and—thanks to Samantha Bellomo's glorious choreography—dancers.

Knee develops the inevitable romance skillfully. Anna leaves Henry more than once and we know she'll return (hey, there's no other actress in the program!), but the script, Harriet Power's insightful direction, and the cast's detailed performances create genuine suspense.

For Anna, dancing is one step among many toward independence; she's befriended by radical feminists (in 1911, that means wanting to vote and smoke) and deserts her safe fiance for an alluring European. For Henry, dance is an end in itself—he neglects everything in devotion to his dream.

Henry's goal isn't fame or fortune, but the purity of artistic creation. He explains the fox-trot to Anna: "I call up the fox in me, show my teeth, wag my tail." Sometimes his dances seem absurd, but they're clearly his own, developed from keen observations of everyday life, not formal training.

We see Anna develop the same sensibilities—"where I work, my feet move to the rhythm of the machines"—and their complicated connection deepens. Knee incorporates comedy, especially Henry's disastrous tryouts for Anna's replacement and his scheme to achieve instant notoriety by dancing off a cruise ship into the Hudson, but Power's superb production focuses on the play's uplifting themes of creativity, perseverance and risk.

Their efforts are aided by the lovely brick-and-hardwood set, the gentle lighting and the costumes, which subtly mark Anna and Henry's growth. Syncopation, like the ballroom dance it celebrates, shows that hard work and big dreams can result in joyful magic.

SYNCOPATION Through April 9, Act II Playhouse, 56 E. Butler Ave., Ambler, 215-654-0200, www.act2.org