I reckon everybody has a breaking point, and mine happened over a plastic Target bag that was cutting into the fingers of my right hand.

The dog walker had just handed me Pepper’s leash by the driveway gravel and mentioned the pretty lady who stays over when Dan works late.

I was standing right there with Dan’s allergy medicine inside that bag, trying to figure out what language Trevor was speaking.

Dan and I had been married fourteen years.

Pepper was our old black lab, eleven years old and very particular about her routine, which mostly involved barking at the mailman and sleeping on the braided rug by the television.

I hired Trevor because Dan traveled two nights a week for his medical supply job, and my shift at the public library down on Main Street ran until seven on Tuesdays and Thursdays.

Trevor was twenty-three, polite in that slouchy way boys that age are, and he always left little notes stuck to the refrigerator about Pepper.

Peed twice, he wrote on Tuesday. Barked at a stroller. Ate grass like a goat.

That Thursday he saw me pull up in my Civic and looked genuinely relieved to hand off the lead.

I almost left the leash inside, he said, shifting his weight from one sneaker to the other, but the lady was on a call in the den.

I thought he meant my sister Janice, who sometimes drops by to pick up mail when we are out of town.

What lady, I asked.

He blinked down at his phone.

The pretty one. Blonde. She stays over when Mr. Dan works late.

The plastic handle of the Target bag bit deeper into my skin.

I asked how she got in.

Trevor looked toward the front porch like he wished a sinkhole would open up right there by the azaleas.

She has your spare key, he said. The blue one with the flamingo on the rubber cap.

My mouth went bone dry.

That key was supposed to be tucked inside the little ceramic frog on the back patio.

I had hidden it there the previous autumn for my mother after her knee surgery, just in case she needed to let herself in while I was at work.

I thanked Trevor. I even tipped him an extra ten-dollar bill because he looked like a kid who was figuring out he had just dropped a bomb and didn’t know how to run from the shrapnel.

Then I put my car in reverse, drove around the corner, and parked behind a large maple tree where I could see my own kitchen window through the windshield.

At 5:17, a silver Honda Civic pulled straight into my driveway.

A woman got out carrying a quilted overnight bag and a square white box from the Kroger bakery. Not flowers. Not wine.

Cake.

Like she owned the place.

She walked right up to the back door, reached behind the ceramic frog, and used the blue flamingo key without a second of hesitation.

I sat in my sedan and stared at my own front door clicking shut behind her.

I did not run inside screaming. I did not honk the horn.

I pulled my phone out of my pocket and called my friend Ellen, who is a family court paralegal in Lincoln and has never once asked a stupid question when someone is calling her from the edge of a cliff.

Do you have somewhere to stay tonight, she asked me.

I said yes. I have my sister’s spare room.

Good, Ellen said. Now don’t warn him. Let him walk right into it.

The house smelled completely different when I unlocked the front door at 6:02.

It smelled like a vanilla candle from the mall and an unfamiliar perfume, sharp and powdery like cheap laundry detergent left out in the sun.

Pepper thumped her tail once from the hallway, slow and heavy, like she was embarrassed for all of us.

The woman was standing right in my kitchen.

My kitchen.

She had taken down my rooster mug, the one my daughter bought me at Cracker Barrel two summers ago, and was stirring coffee with the silver-plated spoon from our sugar bowl.

She turned around and froze with the spoon in mid-air.

I said hi. I am Laura.

She set the spoon down very carefully on the counter, making a tiny ceramic clink that sounded loud in the quiet house.

Dan said you were in Springfield for the library conference, she said.

I looked past her shoulder at the square bakery box sitting on the island.

Happy birthday, D, was written across the top in wobbly blue icing.

Dan’s birthday was not until November.

That was the first real clue this had been going on long enough for them to have their own private calendar and their own private jokes.

She told me her name was Camille Voss. She said Dan told her we were practically separated in every way except on paper and pity.

I laughed once, but it came out sounding like a dog choking on a bone.

The real twist of the knife was Pepper.

Camille crouched down by the island and made a little clicking noise with her tongue. Hi, Peppy girl, she said, just like she had said it a hundred times before when I wasn’t there.

And my dog walked right over to her.

I know that sounds small to anyone else. It wasn’t. That dog wouldn’t even let the plumber touch her ears, but she leaned her heavy black head right against Camille’s knee.

I walked down the hall and found a drawer in the guest bathroom pulled half open. There was a pink toothbrush, a bottle of contact solution, and a tube of coconut lotion that Dan had once complained gave him a migraine when I wore it.

I went into our bedroom and found our framed wedding photo turned facedown on the dresser, looking like an old piece of trash waiting for the bin.

That was when my hands started to shake so hard I couldn’t hold my car keys.

Then Dan’s pickup truck crunched down the gravel drive.

Camille came walking out of the kitchen, her face pale, and whispered right past my ear.

He doesn’t know I still have the key, she said.

I turned around to look at her, my chest tightening until I could barely drag air into my lungs.

Still, I said.

She opened her mouth, looked past me at the front door as the deadbolt started to turn, and said words I never expected to hear in my own hallway.

Laura, she said, her voice dropping to a harsh whisper, I need to tell you who I was before you married him.