The alert came up while I was sitting at a red light, eating a gas-station granola bar: "Unknown tracker detected moving with you."

I almost dismissed it. My phone was always crying wolf about something. But the little map on the screen showed a tiny dot riding along beside my own, and the dot had been with me, it said, for the last six days.

I am not a paranoid person. I am the woman who leaves her doors unlocked and her keys in the bowl by the door. But something about that sentence, moving with you, made the hair on my arms stand up. I pulled into a grocery store lot, put the car in park, and started feeling under the seats.

It took eleven minutes. A flat little disc, the kind people clip to their keys so they can find them, wedged into the seam of the spare-tire well under the trunk liner, taped down so it wouldn't rattle. Someone had thought about the rattle. That detail bothered me more than the device itself.

I sat in the parking lot holding it in my palm like a tick I'd pulled off my own skin, and I went through the obvious list. A jealous stranger. A mechanic. A prank. But the tape was the kind we kept in the kitchen drawer, the green painter's tape Cyrus used for everything, and the dread settled into something colder and more specific.

I didn't confront him that night. I wanted to be wrong. I cooked dinner and watched him chew and laugh at something on his phone, and I studied his face the way you study a word that has stopped looking like a word. The next morning I set the tracker on the kitchen counter, on top of the green tape, and waited.

He came in, saw it, and his whole body changed. Not guilt. Indignation. He picked it up, turned it over, and said, "So now you know."

"Now I know what?"

"I planted it." He said it like a man laying down a winning card. "Because you've been lying to me for months. The late shifts. The 'errands.' You think I haven't noticed? I needed proof, Cyrus needed proof, before I said anything and looked crazy."

He kept talking, building his case, and the strangest thing happened. Part of me almost bought it. He was so sure. He listed times I'd come home late, a receipt he'd found, a coworker's name he'd decided meant something. He had clearly rehearsed this. He had been rehearsing this for a while, and that was the thing that finally cleared my head, because innocent men don't write closing arguments.

"Okay," I said. "If we're doing this. Show me your phone."

The indignation flickered. "What?"

"You tracked me for a week and decided I was guilty. Fine. Let's both be transparent. Give me your phone, unlocked, right now, and I'll give you mine."

He laughed, but it came out wrong, a half-second too late. "I'm not playing this game. You don't get to flip it around because you got caught."

"I'm not flipping anything. You want trust. Phones on the table. Easy." I put mine down, screen up, passcode entered. It sat there glowing between us.

He didn't move. He looked at the phone in his hand the way I'd looked at that tracker in the parking lot, like it was something dangerous attached to his body. And in that silence, the whole architecture of his accusation collapsed, because a man who planted a tracker to catch his cheating wife would slap his phone down on the table without a second thought.

"Why did you really put it in my car, Cyrus?"

It came out of him in pieces over the next hour, the way these things do. There was a woman named Dahlia. There had been for almost a year. They were careful, but careful people get sloppy, and he'd started to worry that I'd notice the math, the missing hours, the mileage, the times the story didn't line up. So he put a tracker on me. Not to catch me. To know exactly where I was at any moment, so he'd never get caught himself. So he could always be one step ahead of a wife who might come home early, or call when he said he was somewhere he wasn't.

The accusation hadn't been a clue he'd found. It had been a costume. He'd built an entire imaginary affair for me so that, if I ever found the device, I'd be too busy defending myself to ask the only question that mattered. He'd spent months researching my supposed betrayal because it was easier than looking at his own.

I kept the tracker. It's in a drawer now, that ridiculous little disc that thought it was so clever. He'd been right about one thing, in the end. It told me exactly where I was. I was married to a man who'd rather follow me into a trap than walk out an honest door.

The dot doesn't move with me anymore. Neither does he.