Jefferson Mays, who has just begun to bowl people over at the Lyceum Theatre in a one-man performance of about three dozen characters, is a Broadway anomaly. His power over an audience - he makes even a one-line character in I Am My Own Wife, which opened Wednesday, believable - comes not from Gattling-gun cadence or knock-'em-dead bravura, the stuff of much Broadway legend.

It grows instead from an understated, meticulously measured performance that has the passion of simple, quiet truth. This is a challenge for an actor whose chief portrayal is a real-life German transvestite who managed to survive the Nazis, and then the East German Communists. The character could lend itself easily to flamboyance, a frantic sort of pace or, worse, a grotesque joke.

But Charlotte von Mahlsdorf was no drag queen and no joke, and Mays imbues her with a vigor that comes from sincerity. Von Mahlsdorf - he was born Lothar Berfelde - died last year at age 74, after a rich and rough life. When a lesbian aunt recognized young Lothar's penchant for women's clothes, she encouraged him to be himself. From then on, Lothar lived as a woman.

She became a collector of German furniture and paraphernalia from the 1890s and stored it in her home, in what became East Berlin. The enormous collection included an entire gay bar that the Communists were about to seize. She operated the museum over three decades; people would come, and von Mahlsdorf would entreat them to share her appetite for great craftsmanship - and for saving history by collecting it.

Mays plays her in black, which von Mahlsdorf wore - a long, workaday dress, head-wrap and orthopedic shoes, set off by one string of pearls. Whenever Mays' character shifts to von Mahlsdorf, his face changes subtly but surely.

The eyes widen into large beads, the mouth thins; his body becomes rigid and the manner, sensible. In Mays' depiction and Doug Wright's script, von Mahlsdorf is no prude, but she is solidly prim; other accounts suggest she had a sensible public appearance and an expansive carnal life.

Von Mahlsdorf was clearly her own woman, and Mays brings her to the stage with a sense of purpose. He seems to specialize in sense of purpose, which gives instant credence to his portrayals of such varied characters as a violent Nazi father, a nurse who calls with bad news or a pompous talk-show host.

He performed the show this past spring at Manhattan's Playwrights Horizons, whose mission is to develop new works, and it reaches Broadway with a thoroughly deserved buzz.

Mays is alone onstage, physically, but three spirits are with him in every scene. One is Wright, who wrote the play and the movie Quills (about the Marquis de Sade) and became entranced with von Mahlsdorf. Wright interviewed her many times in 1992 and 1993, and kept up an acquaintance. He was faced with a dilemma: how to portray a character he respected but who, he learned, may be greatly flawed because she aided the Communist secret police.

Wright handles this with deftness and honesty, by inserting himself as a major character. This makes I Am My Own Wife a play not just about von Mahlsdorf and collecting history, but also about the pitfalls of writing a profile and the vagaries of painting one person in many colors. The play's complexity is a joy to fathom.

You could call I Am My Own Wife theatrical journalism - a form perfected in The Laramie Project, a play written and directed by Moisés Kaufman about the gay-hate killing of Matthew Shepard in Wyoming in 1998. Kaufman directs I Am My Own Wife, giving it the feel of real people in real situations in real time. (And come June, probably, real Tony Awards.)

The third creative spirit on stage with Mays is David Lander, whose lighting design is almost a character in its own right, the only one that Mays himself cannot play. The actor brings the play alive; Lander's precision lighting honors its inherent vitality. The entire enterprise celebrates lives fully lived.