Inara swims in long, slow loops through the dark water. As it ripples and eddies over her skin, the surface of the black lake blossoms with alien light. It surrounds her with color, pure and lurid as a stained glass window: leaf green, saffron, electric blue. This is a biological oddity of the lake. It can be quantified and explained, I know it: there are microscopic organisms in the water, which respond to pressure by emitting a phosphorescent discharge. But the spectacle has crippled my ability to rationalize and diagnose, and in my secret heart, I truly believe that this iridescent flow of sparks comes from Inara – that she is blessing the lake with her radiance.

"You don't swim, Mr. Tam?"

Her voice – deep, sweet, sophisticated – rings out across the lake. I wonder if she learned to speak like that for her career: that indefinable accent, that musical measure of ebb and stress, must be an asset to her work. Maybe, before she became a prostitute, she said "ain't," or "liberry". Maybe she spoke through her nose, or had a laugh like a mule. Somehow, I don't think so. No matter how I try to deconstruct her charm, I come back to the fact that Inara's grace radiates from her core, that there is nothing theatrical about it. She is ineluctably, dangerously wonderful: an anomaly, a miracle, a proof that those terms are slippery, and prone to overlap.

"Maybe later," I say, using my own carefully cultivated cool. "Someone has to play lifeguard."

She laughs.

"Mr. Tam," she says, "you're too cautious."

"Someone has to be," I say, numbly, aware that I'm repeating myself.

Cautious, careful, responsible: those terms can overlap too.

Inara stretches her arm to me. Her palm unfolds like a flower. She lowers it, gently, like a dancer, and begins to swim toward the shore.

Romance is a series of neurochemical processes. It's induced by the production of phenylethylamine, also known as PEA. Phenylethylamine is a stimulant, similar to amphetamines or "speed" in its chemical composition. It induces intense euphoria, and it is triggered, mysteriously, by the presence of a particular person. Scientists are still not quite sure why some people trigger PEA responses in each other. But when we speak of being "in love," we are almost invariably referring to the PEA high: all-night talking and sex jags, willingness to sacrifice work or social priorities for the sake of the beloved, heightened sensory perception (why do birds suddenly appear every time you are near? you make me feel shiny and new! mere alcohol doesn't thrill me at all, but I get a kick out of you, and so on). PEA is addictive, and so it also inspires the desire to stay in the company of the beloved, where one can be assured a steady production of PEA and a consistent high.

Here's the bad news: the PEA high lasts for three years, tops. Most relationships also end within a three-year span. Love without chemical encouragement is relatively dull; it relies on feelings of comfort, familiarity and friendship, and many people leave these sober relationships in search of someone new, someone who can trigger a fresh flow of PEA and start the cycle over again. PEA addicts are common, and they frequently wreak exquisite havoc on their own lives and on the lives of their families. They are, quite literally, love junkies.

I am a very smart man, and this is what I know. It hasn't helped me at all.

Inara spreads her small, delicate hands on a shelf of stone and arches her back, bringing herself out of the water. She lies there for a moment, belly-down on the cool rock, watching me. I offer her a robe. (In the moment before she entered the water, she put it in my hands. It had been warm from her body. It had smelled of vanilla and skin. Had is the word I think of here, implying a moment of possession, however brief, which has slipped into the past.) She wraps the paper-thin silk around her frame and shakes her still glittering hair. I think of mermaids, of certain Pre-Raphaelite paintings: lovely fish ladies embracing lost sailors, drowning them in love.

"You're very sweet," she says, offering me a smile – one of her slow, closed, mischievous smiles, the kind that I don't know how to read.

"We shouldn't be here," I say.

"Why on earth not?"

"Don't you have rules? About being alone with – men? I mean, don't you have to…"

"To charge for this?" Inara says gently. "As a rule, I take money in exchange for sexual services – which, as you've no doubt noticed, I haven't offered tonight."

"I'm not asking – anything of you. I don't want you to think that."

That much is true. Inara is a friend of the family, a connection I don't seek to fathom. She's been invited to spend a lunar cycle at our summer home on the lake, in a strictly unofficial capacity. It would seem less than gracious to impose myself upon her.

"Being here with me tonight," I say, " It's a charged situation, and if you – if we were to – if there were an interest…"

Inara, listening to me ramble, smiles. The gesture seems unreasonably merciful, condoning the broken phrases that spill from my mouth.

"Simon," she says, "are you asking me if we can date?"

"I don't – I mean – I want to be your friend."

In the space between one moment and the next, their overlap, Inara puts her fingers over my lips. Her hand is soft and cool against my face. In the space between her skin and mine, drops of the lake are shining.

"You can be my friend," she says. "My companion."