Champagne flute in hand, I stood with my two best friends at the front desk of a resort in Punta Cana, Dominican Republic, confronting the situation with our room.

The hotel wanted to give us a room with two beds. "We'd rather have a king size," my best friend said.

I stood by with her husband, letting her do the talking. The three of us had been best friends for six years, since college. They'd been married four years that week. Standing there with them, sweating in the hotel lobby, amused at the concierge's confusion, nothing felt more right.

Just a few months before the trip, over a long weekend, all three of us had slept together like three spoons, her in the middle. It was her idea — she said she wanted the closeness. I thought it was sweet. It felt entirely natural to be in such close physical proximity to the two people I had often felt emotionally closest to.

She dressed me up in costumes — then asked me to make out with her while her husband watched and made suggestions.

Inevitably, we all got drunk the next day. Fueled by alcohol and the spirit of the weekend, she took things up a notch and showed me their sex toy collection. She dressed me up in costumes — then asked me to make out with her while her husband watched and made suggestions.

When I left, I wanted more. It seemed like we all did. It made the implausible seem possible.

By the time we were vacationing together, they had introduced me to the concept of a "unicorn" — a bisexual person who could join an existing couple without threatening their relationship. I wasn't sure the definition fit me, but I was willing to give it a try.

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That summer things progressed even further: We moved into a studio apartment together. Granted, he was only there part-time, holding down a job in another state. But she and I did everything together, from planning meals to planning a future. She slept curled around me in bed and we shared an easy physical affection (she'd often email him during the day to suggest including me in their foreplay). But it wasn't just physical — we even built detailed daydreams about the three of us living together full-time.

But there were some awkward moments too — some indication that not everything was OK. When I picked him up from the airport to spend a week with us every month, she'd often ask me to wait in the car before coming home — while they had sex. Sometimes, they also had sex in the bathroom while I was in our shared full-size bed. I pretended it didn't bothered me.

Then, one morning in July after she left for work, he turned to me in the bed we all shared, slid his hand up my stomach, and said, "I could trace the lines of your body all day." When he kissed me, I didn't say no. He said we could keep going and I said yes. Then he said he didn't think we should tell her.

"She won't like it," I told him.

"I'm not going to go any farther with you than she has," he said, although he immediately did. I consented to that too.

That fall, I lived alone while they went back to school. They talked about a future with me in it but made their plans without my input. I struggled with how distant our reality seemed from the dreams we'd shared. When I reached out to talk about it, only he answered. This was also not the "unicorn" way — I was supposed to be "easy" and not cause problems for the couple. But I deserved to know where this was going and I wanted to feel included, like a valued part of their relationship.

Eventually he told me, months after she told him, that she didn't want to include me in their sex life anymore. But I didn't know where that left me — I still wanted to be with them. So I did the next best thing to stay involved: I tried on the idea of being someone's mistress. I clung to him and his talk of a long-term relationship with me.

'She won't like it,' I told him.

For six months, he and I were secretly having weekly video chat sex during her night class, talking on the phone on his way to or from work, or exchanging daily Snapchats and emails.

I never asked him to leave his wife for me. To me, they were still a package deal. I knew I didn't want to give up either of them, but I was terrified of losing him. I wanted him to be mine, I told him, but I didn't need him to be all mine. If she'd ever asked, I would have said I felt the same way about her.

The week after Christmas, he called it off. He said our relationship was destroying him. He asked if we could stay friends "without all the sexual stuff." I said no. I said I could no longer keep his secret. I finally demanded he tell his wife what he'd told me: that he wanted both of us. I said I could share if she could.

That night I got a text from him: She said no. I never spoke to her again and he stopped responding to me soon after.

"Please don't throw me away," I begged him during our last conversation, knowing they already had.

Much later, my therapist would tell me this was a complicated arrangement that required emotional transparency between the three of us, something we could never successfully do. They wanted the appearance of a conventional marriage. I wanted more than to be a toy.

Ultimately, what they offered me really wasn't enough. Even if there were two of them.

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From: Marie Claire US