For a while I thought it might have been that afternoon I burned my black dress in the sink—I’d seen it in a movie once, and when we got home from the funeral, it seemed like the right thing to do, but I didn’t think about the smoke, which scared you, or how mad Mom and Dad would be when they came back because the dress was new and I was putting you in danger. Do you remember?

The girls dance and dance and dance to Paul Simon’s Graceland in the dining room, working themselves up into a frenzy, while their mom makes oatmeal fudgies in the kitchen for them to take for Labor Day to school

Then Zoe, wanting to hear I Know What I Know again, goes and plucks the needle off the record, resulting in a scratch. Amy leaps in and snatches the record away. A scuffle ensues. Zoe bursts into tears. Amy lets the record droop down a little in her hands. Zoe sniffs, purses her lips, and looks back and forth between Graceland and her sister’s face.

Then she lunges forward and pries at the record with all her might until it snaps in half.

In the stunned silence that follows this, before their mother comes in and screams at them that this was a library record and that now they’ll have to pay and go to your room, Zoe looks at Amy, and Amy looks directly ahead, at the two rows of four plates that hang from the white wall. Each plate features a ghost ship, which their mom has explained is when a ship sinks and all its traces disappear into the sea. And it’s like people who die but don’t get buried: the ships turn into ghosts. Sailors see them floating out on the water, aflame. Of the eight plates six of them are half-obscured by bright orange fire.

If Amy could go back a few seconds, she would break the plates with her sister, one by one, rather than the record, which was something they loved and now will never have again.

Amy is the tallest kid in her grade, and the fastest, and the best at math

She comes first during roll call and gets only straight As. Their school uses a Japanese kind of math called Kumon that lets you do however many problems you want in an hour. Amy likes to do a lot of problems without making mistakes. All the other kids disappear when she starts doing her Kumon. All she is aware of is those numbers. She loves numbers and letters and practices her handwriting every evening at home.

One day in the middle of long division a hand reaches inside her bubble and attaches itself to hers. Amy gasps without meaning to. She looks up and sees the principal.

Most children dread the appearance of the school principal at their desk, but Amy is so well behaved that it does not occur to her to worry. When the principal asks her to come outside with her please, Amy politely declines. But then when she sees the stunned scandalized eyes of the principal she puts her pencil down.

In the back of the ambulance, her sister has been taken over by a ghost

Their mom gets as strong as a superhero and holds her down. Amy has no idea what is happening. A few minutes ago she was still inside a bubble, organizing numbers, and now her sister has been taken over by a ghost. Amy had always assumed it would be fun to ride in an ambulance or a fire truck or a police car because you would get to go fast and break all the rules and not stop at any lights. But everything is wrong now. Zoe throws up but doesn’t know she’s throwing up, so the throw-up just drips down her chin and onto the lavender-colored dress that used to be Amy’s that they’d gotten from a friend, and the lady who works for the ambulance mops it off her, but Amy fears that the towel will scratch her sister’s face.

Zoe’s eyes, always big and brown and sparkly as the campfire, are white. Her body jerks to one side at a rhythm that is not a human rhythm. Amy screams, Zoe, Zoe, Zoe, but Zoe isn’t there. Their mom gets angry and says to shut up because she’s making everything worse. Then every fiber of Amy’s body screams, in silence. Zoe, Zoe, Zoe.