The afternoon I discovered my husband was sleeping with my sister began with a permission slip.

That is the detail I remember most clearly.

Not because it mattered afterward, but because it had mattered so much fifteen minutes earlier.

My nine-year-old daughter, Lily, was going on a fourth-grade field trip to the science museum, and the permission form had to be returned by three o'clock.

She had reminded me at breakfast.

"Mom, please don't forget."

"I won't."

"You forgot the library form last month."

"I remembered eventually."

"After Mrs. Patterson emailed you."

"Details."

Lily had smiled, but before getting out of the car at school she pointed at me.

"Three o'clock."

"Three o'clock."

"Promise?"

"I promise."

At the time, breaking that promise seemed like the worst thing I might do that day.

My name is Hannah Mercer.

I was thirty-five years old, thirteen years married, twenty-four weeks pregnant, and already the mother of four children.

Lily was nine.

Noah was seven.

Sophie was five.

And Jack had just turned three.

Our fifth baby was supposed to arrive in October.

Another girl.

We had already picked the name Grace.

My husband, Daniel, suggested it.

"Grace Mercer," he had said one night while we were lying in bed. "Sounds right."

I had put his hand on my stomach.

"Grace Evelyn Mercer."

"Your grandmother would like that."

"She'd complain we didn't use her first name."

"Your grandmother complained about everything."

"True."

The baby kicked beneath his palm.

Daniel smiled.

I remember that smile now.

I wish I didn't.

That Wednesday morning had been completely ordinary.

Daniel left early, supposedly for a client meeting.

I packed lunches, found Noah's missing sneaker beneath the couch, negotiated with Jack over whether pajamas counted as clothes, and cleaned strawberry yogurt from Sophie's hair.

At eight fifteen, I got everyone out the door.

At eight seventeen, Sophie announced she had forgotten her water bottle.

At eight twenty-two, we finally left.

After school drop-off, I went to my obstetrician for a routine appointment.

Everything looked normal.

The baby's heartbeat was strong.

My blood pressure was slightly elevated, but not enough to concern the doctor.

"Try to rest more," she said.

I laughed.

She knew I had four children.

"I'll schedule that between laundry and the apocalypse."

"I'm serious, Hannah."

"I know."

She smiled.

"Twenty-four weeks. You're doing well."

I left with a little printout showing the baby's profile.

I put it in my purse.

Then I went grocery shopping.

Milk.

Eggs.

Apples.

Pasta.

Chicken.

Peanut butter.

Cereal.

The same boring things I bought every week.

Halfway through the frozen-food aisle, I remembered Lily's permission slip.

It was sitting on the kitchen counter beneath a yellow magnet shaped like a lemon.

I checked the time.

1:47.

Plenty of time.

I finished shopping, loaded the bags into our SUV, and drove home.

Daniel's car was in the driveway.

That surprised me.

He was supposed to be at work.

I assumed his meeting had ended early.

I even felt pleased.

Maybe we could have coffee together before I went back to school.

That thought embarrasses me now.

I parked beside him.

I carried three grocery bags through the garage.

The house was quiet.

Then I heard Daniel talking.

He was in the living room.

His voice was low.

Warm.

Intimate.

The voice he used to use with me.

"Baby, I love you."

I stopped.

The grocery bags pulled against my fingers.

For a second, I genuinely thought I had misunderstood.

Maybe he was talking to Sophie.

Except Sophie was at school.

Maybe he was leaving me a message.

Except he knew I was shopping.

Then he laughed.

Not his normal laugh.

A private laugh.

"I know. Me too."

I stood in the hallway.

My heart began beating harder.

I could see only part of the living room from where I stood.

Daniel was sitting on the couch with his back partly toward me.

His phone was against his ear.

"I'll see you later," he said. "Same place."

Pause.

"No, she won't know."

My body went cold.

Another pause.

Then Daniel laughed again.

"Trust me. I'll come up with something."

I stopped breathing.

"I've been doing this for a year. She believes everything I tell her."

The glass pasta sauce jar inside one grocery bag pressed against my wrist.

I barely noticed.

Daniel said something else.

Then:

"Because she's an idiot."

He laughed.

My husband laughed.

The man who had watched me give birth four times.

The man who had slept beside me for thirteen years.

The man whose daughter was moving inside my body.

He laughed because another woman apparently found it funny that I trusted him.

A glass jar tapped another jar inside the bag.

Click.

Daniel turned.

Our eyes met.

His smile disappeared.

The phone remained against his ear.

Neither of us moved.

There are moments when your mind protects you by becoming stupid.

Mine did.

I looked at his phone.

Then at him.

Then toward the kitchen.

I actually thought:

Maybe there's an explanation.

I needed one.

Anything.

A joke.

A misunderstanding.

A conversation about somebody else.

A stupid prank.

Some context I had missed.

Daniel slowly lowered the phone.

"Hannah."

The woman on the other end was still speaking.

I could hear a faint voice.

Daniel ended the call.

I put the grocery bags on the floor.

Not dramatically.

My hands were shaking so badly that I knew I would drop them otherwise.

One bag tipped sideways.

An apple rolled across the hardwood.

Daniel stood.

"Why are you home?"

That was what he asked.

Not are you okay.

Not let me explain.

Why are you home?

I looked at him.

"I forgot Lily's permission slip."

He rubbed his forehead.

"Oh."

I waited.

He looked annoyed.

That was almost worse than panic would have been.

"Who were you talking to?"

"Hannah—"

"Who?"

He walked toward me.

I stepped backward.

"Don't."

He stopped.

"Okay."

"Who were you talking to?"

"It's complicated."

"No, it isn't."

"You heard part of a conversation."

"I heard you tell a woman you love her."

He looked away.

"I heard you tell her you'd meet her at your usual place."

Nothing.

"I heard you laugh because I'm stupid enough to believe your lies."

His face tightened.

"I shouldn't have said that."

I stared at him.

"That's the part you're sorry for?"

"No."

"Then answer me."

He exhaled.

"I've been seeing someone."

The room seemed to tilt.

I put one hand against the wall.

My other hand automatically moved to my stomach.

Grace kicked.

A small movement.

Normal.

Alive.

"How long?"

Daniel did not answer.

"How long?"

"A while."

"What does that mean?"

"Hannah."

"A month?"

"No."

"Three months?"

He looked down.

"Longer."

"Six?"

Silence.

My stomach turned.

"How long, Daniel?"

"About a year."

A year.

I thought about birthdays.

Christmas.

Thanksgiving.

Our anniversary.

The family vacation to North Carolina.

The night he took me to dinner after I told him I was pregnant.

A year meant hundreds of mornings.

Hundreds of lies.

I whispered, "Who?"

He looked at me.

Something changed.

Until then, Daniel had seemed ashamed.

Now he looked afraid.

That frightened me.

"Who is she?"

"It doesn't matter."

I stared at him.

"It doesn't matter?"

"I mean knowing isn't going to help you."

"Who?"

"Hannah, please."

"Who is she?"

He turned away.

I followed.

"Is she married?"

"No."

"Do I know her?"

His shoulders stiffened.

My heart stopped.

"Daniel."

He said nothing.

"Do I know her?"

"Yes."

I thought of women from his office.

Neighbors.

Friends.

Mothers from school.

I hated myself for mentally searching through them.

"Who?"

He rubbed both hands over his face.

"Please sit down."

"No."

"You're pregnant."

"I know I'm pregnant."

"Your doctor said—"

"Do not use my pregnancy to avoid answering me."

He closed his eyes.

"Who?"

Finally, he looked directly at me.

"Rachel."

I stared at him.

The name meant nothing for perhaps half a second.

Then it meant everything.

Rachel.

My younger sister.

"No."

Daniel swallowed.

"I'm sorry."

"No."

"Hannah."

"Don't."

I stepped backward.

"Don't say her name."

He moved toward me.

I raised my hand.

"Stay away."

He stopped.

"You're lying."

"I'm not."

"Yes, you are."

"I wish I was."

"Rachel?"

He nodded.

My sister was three years younger than me.

Thirty-two.

I had braided her hair before school when we were children.

I had taught her how to drive in our father's old Honda.

When her first serious boyfriend dumped her in college, she slept in my apartment for two weeks.

When she lost her job at twenty-seven, Daniel and I let her stay with us.

She had a key to our house.

She knew my children.

They called her Aunt Rachel.

She had attended every birthday party.

Every Christmas.

Every Thanksgiving.

She had sat beside me at my baby shower three months earlier.

She had put one hand on my stomach and said, "This little girl is going to be so spoiled."

I ran to the downstairs bathroom.

I barely reached the toilet before vomiting.

Daniel stood outside.

"Hannah?"

"Go away."

"I need to make sure you're okay."

"Go away!"

He did not.

I could see his shoes beneath the door.

I sat on the bathroom floor.

My hands shook.

I kept touching my stomach.

Grace moved again.

I whispered, "You're okay."

I don't know whether I was speaking to her or myself.

When I finally opened the door, Daniel was still there.

His eyes were red.

I hated him for looking sad.

"How?"

He frowned.

"What?"

"How did it start?"

"I don't think—"

"I want to know."

He leaned against the wall.

"It wasn't planned."