Susan had spent the better part of a year telling me those Denver trips were strictly for business. She was so sure of him, and honestly, who could blame her? Michael was a regional director for a medical-supply firm, and he had that easy, winning way about him that made you feel like you were the only person in the room.

We were at the winter gala in a rented ballroom in Overland Park. It was fancy, lots of velvet curtains and soft, golden lighting, and Susan looked absolutely beautiful in her navy dress with her grandmother’s little pearl studs in her ears.

Michael had been busy working the room for nearly forty minutes. He was over by the bar, laughing a bit too loud at some man in a bow tie, his hand resting on shoulders like he owned the place. I sat there with Susan, sipping a little sparkling cider, watching her watch him. She had this way of looking at him that reminded me of a woman checking a stove she wasn’t entirely sure she had turned off. It was a subtle thing, but it was there, a little flicker of unease buried under the sequins and the small talk.

Then, a man I didn’t recognize approached our table. He looked tired, the kind of tired that sleep doesn’t fix. He wasn’t a guest I’d seen earlier, and he didn’t have a name tag. He stopped right in front of us, and for a second, the whole room seemed to get quiet, even though the music was still playing.

“You must be Susan,” he said. His voice was steady, but there was a tremor in his hands. “I’m Gerald. I think your husband and my wife have gotten very close on those Denver trips.”

Susan’s champagne glass stopped halfway to her mouth. She didn’t move for a long time.

The air felt thin, like the oxygen had been sucked out of our corner of the ballroom. I didn’t know what to do, so I just stood up. I reached out and put my hand flat on the small of her back. I wanted to give her something firm to lean into, the way I used to do when she was a little girl waiting for a shot at the doctor’s office.

“My wife is Danielle,” Gerald went on, his tone remarkably polite, as if he were discussing the weather. “She coordinates your husband’s trade shows. I only found out three weeks ago. I almost didn’t come tonight.”

Susan set her glass down on the little cocktail table with a sharp click. Her knuckles went white against the edge of the linen cloth. She didn’t look at him at first. She just stared at Michael across the floor. He was throwing his head back, laughing at something an executive said, completely unaware that the ground beneath his wife was splitting wide open.