Chapter 1

My husband's childhood best friend called our marriage temporary in front of fifty people.

Nathan raised his glass to her.

"To the boy who knew me first," Cassidy said, looking only at him. "Girlfriends come and go. Wives do too. But childhood best friends are forever. We share a brain, Nate."

"Always," my husband said.

Their glasses touched.

The room went silent.

I stood three feet away beside the whiskey-and-dark-chocolate cake I had ordered, wearing the smile I had practiced for photographs.

No one looked at Cassidy.

They looked at me.

That was the worst part. Everyone understood exactly which woman she expected to disappear.

I had spent ten weeks planning Nathan's thirtieth birthday. Cassidy needed less than a minute to remind me that, in my own marriage, I was still the outsider.

Earlier that evening, I had given Nathan my gift.

I had spent five months tracking down a restored 1972 Gibson guitar he had been obsessing over since college. When he opened the case, he gave me a polite smile, a quick peck on the cheek, and a casual, "Wow. Thanks, Elise. That's really nice."

Then, he immediately set it aside on a table to go grab a drink.

But when Cassidy walked into the riverfront loft half an hour later, the temperature in the room changed.

She handed him a thick, hand-bound scrapbook.

"Happy birthday, Nate," she said, using the nickname only she was allowed to use.

Every page belonged to the two of them: at sixteen in a battered red Jeep, at their college graduation, on a beach trip. I, his wife, wasn't in a single photograph.

"And I found this," she added, pulling a tarnished brass compass from her purse. "Remember the time capsule we buried when we were twelve? You said you wanted a compass like your grandfather's."

Nathan's eyes filled with tears. He pulled her into a tight hug, ignoring my presence. "Cassidy, this is incredible. You always know exactly what I want."

My stomach dropped. I stared at the restored guitar case abandoned against the wall. Five months of effort hadn't earned a real embrace, yet Cassidy had brought tears to his eyes with a piece of their past.

When the party finally ended and we were home, I confronted him in the kitchen.

"Nathan, Cassidy's speech was way out of line," I said, forcing my voice to stay steady. "She basically told a room full of our friends that our marriage is temporary."

Nathan sighed, violently tossing his tie onto the counter. "Elise, please. Not tonight. Don't ruin a good day."

"I'm not ruining it. She humiliated me."

"She was joking!" he snapped, looking at me like I was a crazy person. "We grew up together, we have history! Why are you always so insanely insecure about my past?"

"I'm not jealous of your past, Nathan. I'm angry about how she treats me in the present."

"You just don't get our dynamic," he snapped. "She's like a sister to me. Stop reading into everything."

He grabbed his glass of water and walked into the bedroom, leaving me alone in the dark kitchen.

My phone buzzed on the counter. It was a Facebook notification.

Cassidy had just posted a picture from the party. It was a candid shot of Nathan hugging her, his face buried in her shoulder.

The caption read: Some history can never be replaced by something new. Happy 30th to my favorite boy.

She didn't tag me. But she made sure everyone else saw it.