The people with the most baroque sex lives, I've noticed, often are the ones who look the most innocent.

Anna meets me at the House of Shields on New Montgomery Street, a few blocks from the marketing company where she works as a graphic designer. (All names have been changed here.) Still in her office clothes, a convservative blouse and pressed black pants, she has a round, sweet face and brown hair pulled back in a ponytail. To look at her, you'd never think that she has attended workshops on enhancing the female orgasm. Or that she, a lesbian, sleeps with both men and women, sometimes at the same time.

But Anna's sexual adventures aren't enough to give zest to her life. Her work is dull, and she feels frustrated. Like so many confined to offices in the city—where everyone seems to paint, dabble in performance art, or at least blog—Anna views her job as a stopgap until she finds her true calling. That might be easier, she thinks, if she changed her social circle.

"I used to hang out with people who talked about doing something," she says as we begin polishing off hefeweizen. "Now I want to hang out with people who actually are doing something."

Her friend Curits is certainly doing something, although maybe not in the way she means. Curtis is a former woman working hard to become a man. For months he—Curtis already identifies as a man—has been taking testosterone shots. His muscles have gained definition, and his upper lip is dusted with peach fuzz.

Curtis and Anna like to play backgammon and have sex from time to time. Essentially, they are "friends with benefits." That phrase seems inadequate to describe the complicated liaison of a lesbian and a female-to-male transsexual. But whatever you want to call it, the relationship is changing. Anna fears that she is becoming indifferent to Curtis.

"When we get together, it's like, 'What shall we do? Shall we shoot pool or shall we have sex?' And I don't really care which." Anna has the kind of romantic problem you find only in San Francisco. She prefers women, and so the more of a man Curtis becomes, the less she wants to sleep with him. In fact, she is more attracted to Curtis's girlfriend, Wendy.

Things came to a head recently, and as we drain the pint glass, details spill across the table. As Anna and Curtis were fooling around at her place in Oakland, she reached for Curtis's breasts, which he had bound flat to his chest. Curtis pushed her hand away. He went down on Ana, but frustration overwhelmed desire. She craved a female body.

Curtis thoughtfully suggested they call Wendy and invite her over to join in, something they'd done before. She couldn't, it turned out. But on the phone, Wendy invited Anna to think about what she'd like to have happen. After they hung up, Anna decided to write it all down.

"Take off your shirt," she told Curtis. She wrote on his back: Don't let me be in control. Scribbling furiously, she covered all of his skin that wasn't hidden by the binding. Call me little girl. Bite my nipples. Spank me.

Perhaps it's the beer, but I find this wonderful—a postmodern love poem written to a woman on her lover's body. And it worked. A few days later, Wendy called, evidently eager to get together again. Anna was thrilled, until Wendy said: "But first, you and I need to have a discussion about boundaries." She wanted to decide in advance who was allowed to do what to whom. They discussed it, but in the end they didn't set a date. And so instead of doing something, Anna found herself again only talking about it.

Anna finishes her beer and stares morosely at the glass. But then her face brightens, and I see that I've not heard the end of the story.

Wendy works as a store clerk by day and as a stripper by night. A couple of weeks after the three-way-that-wasn't, Anna, Curtis, and some friends went to a SoMa bar to see her perform. As Wendy slipped onstage and began to gyrate, Anna noticed that she had the stripper's talent for convincing each spectator that she yearned only for him or her. Leaning against the bar, Anna wondered why she had come.

"I like your jacket."

Anna turned around to find a tall, skinny girl wearing a T-shirt, a tie, and pants emblazoned with black-and-white photos of Paris. "Where did you get it?"

"From the trash." It was a peach plaid blazer that Anna's roommate had found in a pile of garbage on the sidewalk.

"I'm Katie," said the girl. They began to talk. Anna sometimes complains that lesbians only like to talk about haircuts and therapy. But Katie mentioned neither. Confident and smart, she worked in theater and painted in her spare time.

They headed outside for some air. On the way, one of the strippers looked at Katie and said idly, "Ties are for people to grab hold of." Outside, Anna surprised herself. She grabbed Katie by the tie and kissed her. They took a cab to Katie's place and fooled around. Being with Katie was much better than playing backgammon. Starved for female flesh, Anna was voracious.

After a while, Katie asked, "Why are you so good at this?"

"I just pay attention to what your body is telling me," Anna replied. Those courses on enhancing the female orgasm weren't a total waste of money.

Two days later Anna went to see Curtis, home in bed after his double mastectomy. He was groggy from them anesthetic, but happy.

"I'm going to be so hot now," he said, surveying his flat chest. Anna nodded, then caught Wendy's flirtatious glance. It didn't matter. Now there's Katie, who has no boundaries, no body parts Anna can't touch. And Katie is actually doing something.