Invisible Wings.

In Joanna Haigood's latest and most ambitious dance, Invisible Wings, set in the fog-cloaked, wind-whipped bones of San Francisco's Fort Point beneath the Golden Gate Bridge, the choreographer takes on a monumental subject: the Underground Railroad that ferried slaves to freedom before and during the Civil War. She does it with much of the same abstract beauty that she has brought to scaling the San Francisco Ferry Building clock tower or floating fetus-like in a tank of water.

Collaborating with vocal ensemble leader Linda Tillery and her group, along with storyteller Diane Ferlatte, Haigood has built a series of vignettes, from slave ship to runaway slaves, from Southern auction block to plantation house, that form a crazy quilt of antebellum life and the treacherous interface of white and African culture.

Africans, Ferlatte told the crowd, were first separated from tribe and family and imprisoned in forts along the coast until sufficient numbers were corralled to fill a slave ship. To give us a taste of this, we in the audience stood outside the iron doors of the fort as night fell and were separated and bullied into three groups by ushers playing the role of guards. It was an attempt to communicate the terror of the round-ups suffered by West Africans beginning nearly 400 years ago, but it was the night's most misguided and cavalier gesture, an act of amateur agitprop in an evening of otherwise often ghostly poetry.

Invisible Wings slowly moved inside the fort for a number of "moments." The first installation took place in an antechamber. There, a man stood on a pedestal. His hands were manacled and his neck and head were in iron grips, above which was suspended a cow bell The sound of the sea crashed. He writhed and rocked with the rocking of an imagined ship. Candlelight filled alcoves, and the lonely agony of the Middle Passage was quietly made real.

Later, we watched activity framed by the fort's Romanesque arches that line each floor, as though we were peering through the windows of a plantation mansion. Ladders of thirty-seven rungs linked several levels, and as the night progressed dancers moved up and down, hung from rungs, and leapt to freedom. The ladder as a material bridge for the spirit had never seemed so clear.

Some vignettes were murky. As compelling as she is, Shakiri, playing a hawker of eight-dollar shoes, was an oddity. The link to the auction block was too obvious and a shoe auction as a metaphor for economic life dependent on African sweat too imprecise. The vocal ensemble was also frequently jarring. With modern head mikes that constantly crackled and garbled their voices, and a dramatic presence that begged for the spotlight, the singers too frequently broke the spare mood. Often it felt as though several directors and several visions were competing.

When Haigood seemed in charge of the work, which was commissioned by Jacob's Pillow Dance Festival in Massachusetts for presentation there (an actual stop on the Underground Railroad), Invisible Wings was at its most beautiful and visionary. Haigood showed the horror and the heroism: running in place in bleached light, one arm extended in extremity, the other hand clutching her shawl as the chorus sang "run, Mary, run," her journey an apparently endless test of courage, luck and endurance; the wealthy white man who used his cart and horse to lead blacks to freedom; the spiritual heights to which the enslaved could sometimes soar knowing that other worlds and other realities existed, unbeknownst to their enslavers. While Ferlatte told us the story of the slaves' internal freedom, which could give them the room they needed to endure lives of unimaginable brutality, Haigood sent her dancers soaring overhead on cables. One could almost imagine that the oppressed were free at last.