David Greenspan gives a wild ride of a performance in “On Set With Theda Bara,” and marionettes star in Vaclav Havel’s play “Audience.”The performance space at the Brick, in Williamsburg, Brooklyn, is already veiled in haze when the audience arrives. A long table draped in black runs down the center of the room, lit by sconces and hanging lamps, their soft glow reflected in mirrored walls at either end.There’s a ghostly, expectant feel to it all, as if we’ve entered an alternate plane where specters might be summoned. You wouldn’t be surprised if a séance broke out. Somewhere in the middle of the swirling phantasmagoria that is the play “On Set With Theda Bara,” indeed one will.A certain channeling of spirits, though, begins as soon as the performance does. The actor David Greenspan takes his place at the head of the table, with the audience seated on either side, and becomes the glamorous silent-film star Theda Bara, or a version of her. Identity is slippery in this play, as it was for the actress, who started out as Theodosia Goodman from Ohio but was marketed by Hollywood, under her screen name, as an exoticized Arab.Obsession with her is the gossamer string that binds Theda to the other characters in this campy, comic solo show: Detective Finale, a gay 21st-century gumshoe looking for his missing child; Ulysses, a movie-theater organist enthralled with Theda ever since one of her films aroused him to distraction at the keyboard; and Iras, Finale’s genderqueer 16-year-old, who would become Theda Bara if only that were possible.“The Theda I want to be is like — transgressive but unproblematic, know what I mean?” Iras says. “Like minus the appropriation and stuff.”Greenspan, a virtuoso of multicharacter solo shows, gives a wild ride of a performance, fleet-footed and mercurial but capable of great stillness, too. Stalking, twirling and dancing through the space, even treading on the tabletop, he is quite something to behold, with Stacey Derosier’s lighting finely calibrated to his every move. (The set is by Frank J. Oliva.)Written by Joey Merlo, directed by Jack Serio and presented by the Exponential Festival, this play collides periods and period styles along with storytelling genres. It’s part noir, part vampire tale; a vampire — a predatory woman — was one of Theda’s most famous roles.Like any decent vampire, Theda is undead: 138 years old, by Iras’s calculation, but still looking — Iras tells her when they meet — just as she always did onscreen. Holed up with Ulysses, Theda watches clips from her old movies on YouTube, which she pronounces, adorably, as YouTubah.“Things are strange here,” Ulysses says, and he could easily be speaking of the play. “Reality seems to move about. You’ll be in one place one minute and in another the next. And it’s not only the place that moves but time as well.”In a whipsaw-changeable show that employs just a single costume (by Avery Reed) and almost zero props, it’s not always clear which character is speaking — and the protean Theda has more than one voice. That periodic smudginess is less bothersome than you’d think, though.Only at the very end does the play turn too murky to work. Until then, Greenspan renders it entirely fascinating.Vit Horejs and Theresa Linnihan in “Audience,” a production by the Czechoslovak-American Marionette Theater that is set in a brewery, at La MaMa.Jonathan Slaff“Audience,” a puppet version of an autobiographical Vaclav Havel play at La MaMa, in the East Village, has the opposite trouble: a lively finish, but a glacially paced staging whose intriguing aim is never close to realized.Directed by Vit Horejs, who performs it with Theresa Linnihan, this production by the Czechoslovak-American Marionette Theater is set in a brewery, where a playwright works, rolling barrels. A brewmaster-informant chats him up, hoping for scraps of intel.Two large projection screens are suspended over the playing space. (Production design is by Alan Barnes Netherton.) One screen displays live, black-and-white video from multiple cameras aimed at parts of the stage, to suggest the oppression of constant surveillance. The other shows color close-ups of the performance.In Horejs’s English translation, it’s a very talky two-hander, but the marionettes (by Linnihan, Milos Kasal and Jakub “Kuba” Krejci) don’t have moving facial features, which makes for unfortunately static close-ups. The acting, alas, does not captivate, so the spying never feels real enough to make the surveillance images meaningful.There is a smart video prelude to the performance, though: a sleek newsreel (by Suzanna Halsey) that gives a quick and clever Czech history lesson to contextualize the play. Bit of a disappointment, what follows.On Set With Theda BaraThrough Wednesday at the Brick, Brooklyn; theexponentialfestival.org. Running time: 1 hour 5 minutes.AudienceThrough Feb. 19 at La MaMa, Manhattan; lamama.org. Running time: 1 hour 20 minutes. More