She said, "Dad called me from the building that day."

I pulled away from her.

"What?"

"He called from the building."

"On your cell phone?"

She nodded yes, and it was the first time since Dad died that I'd seen her not try to stop her tears. Was she relieved? Was she depressed? Grateful? Exhausted?

"What did he say?"

"He told me he was on the street, that he'd gotten out of the building. He said he was walking home."

"But he wasn't."

"No."

Was I angry? Was I glad?

"He made it up so you wouldn't worry."

"That's right."

Frustrated? Panicky? Optimistic?

"But he knew you knew."

"He did."

I put my fingers around her neck, where her hair started.

I don't know how late it got.

I probably fell asleep, but I don't remember. I cried so much that everything blurred into everything else. At some point she was carrying me to my room. Then I was in bed. She was looking over me. I don't believe in God, but I believe that things are extremely complicated, and her looking over me was as complicated as anything ever could be. But it was also incredibly simple. In my only life, she was my mom, and I was her son.

I told her, "It's OK if you fall in love again."

She said, "I won't fall in love again."

I told her, "I want you to."

She kissed me and said, "I'll never fall in love again."

I told her, "You don't have to make it up so I won't worry."

She said, "I love you."

I rolled onto my side and listened to her walk back to the sofa.

I heard her crying. I imagined her wet sleeves. Her tired eyes.

One minute fifty-one seconds...

Four minutes thirty-eight seconds...

Seven minutes...

I felt in the space between the bed and the wall, and found Stuff That Happened to Me. It was completely full. I was going to have to start a new volume soon. I read that it was the paper that kept the towers burning. All of those notepads, and Xeroxes, and printed e-mails, and photographs of kids, and books, and dollar bills in wallets, and documents in files ... all of them were fuel. Maybe if we lived in a paperless society, which lots of scientists say we'll probably live in one day soon, Dad would still be alive. Maybe I shouldn't start a new volume.

I grabbed the flashlight from my backpack and aimed it at the book. I saw maps and drawings, pictures from magazines and newspapers and the Internet, pictures I'd taken with Grandpa's camera. The whole world was in there. Finally, I found the pictures of the falling body.

Was it Dad?

Maybe.

Whoever it was, it was somebody.

I ripped the pages out of the book.

I reversed the order, so the last one was first, and the first was last.

When I flipped through them, it looked like the man was floating up through the sky.

And if I'd had more pictures, he would've flown through a window, back into the building, and the smoke would've poured into the hole that the plane was about to come out of.

Dad would've left his messages backward, until the machine was empty, and the plane would've flown backward away from him, all the way to Boston.

He would've taken the elevator to the street and pressed the button for the top floor.

He would've walked backward to the subway, and the subway would've gone backward through the tunnel, back to our stop.

Dad would've gone backward through the turnstile, then swiped his Metrocard backward, then walked home backward as he read the New York Times from right to left.

He would've spit coffee into his mug, unbrushed his teeth, and put hair on his face with a razor.

He would've gotten back into bed, the alarm would've rung backward, he would've dreamt backward.

Then he would've gotten up again at the end of the night before the worst day.

He would've walked backward to my room, whistling "I Am the Walrus" backward.

He would've gotten into bed with me.

We would've looked at the stars on my ceiling, which would've pulled back their light from our eyes.

I'd have said "Nothing" backward.

He'd have said "Yeah, buddy?" backward.

I'd have said "Dad?" backward, which would have sounded the same as "Dad" forward.

He would have told me the story of the Sixth Borough, from the voice in the can at the end to the beginning, from "I love you" to "Once upon a time..."

We would have been safe.