For three months I had no proof, only a feeling that sat in my chest like a swallowed stone.

It wasn't anything you could point to. Marcus came home on time. He kissed my forehead, asked about my day, fell asleep with his hand on my hip the way he always had. But there was a new carefulness to him, a way of turning his phone face-down on the counter without seeming to think about it, a softness in his voice when he said he was "just tired." You can live with a man for nine years and feel the temperature of the house change a single degree. I felt it. And every time I told myself I was being paranoid, the stone got heavier.

I didn't want to confront him with nothing. I'd seen what that did to my sister — the accusations, the denials, the slow erosion until she was the crazy one and he was the victim. I wanted certainty, the kind nobody could talk me out of.

So I bought a small camera online and had it shipped to my office downtown instead of the house. I told no one. It came in a flat brown box, smaller than a deck of cards, with an infrared lens that could see in the dark and an app that pinged my phone whenever it sensed movement. That weekend I tucked it into the soil of the fiddle-leaf fig in the corner of the living room, the big leafy thing I'd babied for years, and I aimed it straight at the front door and the couch.

When Marcus asked about the little glowing dot, I didn't even hesitate. "It's a grow light," I said. "The leaves were yellowing. The lady at the nursery swore by it." He nodded, kissed the top of my head, and never looked at that plant again. He trusted me too much to be suspicious of a houseplant. There's a particular shame in realizing your honesty had become your camouflage.

For two nights, nothing. I started to feel foolish, almost relieved, ready to dig the thing out of the dirt and apologize to no one.

The third night, the app buzzed at 4:11 a.m. I was in a hotel for a work conference two states away. I sat up in the dark and opened the clip with my thumb shaking.

Timestamp 4:07. The room rendered in that ghostly grey-green of night vision. Marcus crossing the living room — no lamp, no phone light, moving the way you move when you've practiced being quiet. He went to the front door, turned the deadbolt slow so it wouldn't click, and opened it.

A woman stepped inside. He put a finger to his lips. She laughed without sound, and he pulled her toward the couch, and I closed the app because I'd seen everything I would ever need to see.

I didn't cry. I'd done all that crying over the past three months, alone, on nothing. Now I had something. I forwarded the file to myself, then to a folder, then to a lawyer's intake form before the sun even came up.

He still doesn't know it was the fig tree. He thinks I hired someone. I let him believe whatever keeps him guessing — the same way I once guessed, in the dark, with a stone in my chest and no one to believe me but a houseplant.