Finally, my mom came upstairs, passing my room to knock on Whitney's door. When there was no reply, she said, "Whitney, honey. Let me in." Nothing. She stood there for what felt like a full minute or two before suddenly I heard the lock turn, and then the door open and shut again.

I went back downstairs, where I found Kirsten sitting at the kitchen table with my father, an untouched grilled cheese on a plate in front of her. "Look," she was saying as I opened the cabinet to pull out a glass, "she explains it all away really well. She'll have Mom brainwashed in three seconds."

"I'm sure that's not true," my dad told her. "Give your mother some credit."

Kirsten shook her head. "She's sick, Daddy. She hardly ever eats, and when she does she's really weird about it. She'll eat one quarter of an apple for breakfast or, like, three saltines for lunch. And she works out all the time. The gym around the corner is open twenty-four hours, and sometimes I wake up and she's gone, and I know she's there."

"She might not be," my dad said.

"I followed her. A few times. She runs on the treadmill for hours. Look, I had a friend when I first moved to the city, her roommate was like this. She got down to eighty pounds or something; they had to put her in the hospital. It's serious."

My dad was quiet for a second. "Let's just get her side of things," he said finally. "And then we'll see where we are. And Annabel?"

I jumped. "Yes?"

"Maybe go finish that homework?"

"Okay," I said. I finished my water, then put my glass in the dishwasher and headed back upstairs. As I forced myself back to parallelograms, I could hear my mother talking to Whitney next door, her voice low and soothing. I was almost done with my work when her door opened.

"I know," my mom was saying. "How about this: Take a shower, and a nap, and I'll wake you up when it's time for dinner. Okay? Everything will look better then."

I heard a sniffle, which I assumed was Whitney agreeing to this, and then my mother was walking past my door again. This time, she looked in at me.

"Everything's all right," she said. "Don't worry."

Looking back, I don't doubt my mom believed this at the time. I learned later how Whitney had completely reassured her, saying she was just overworked and overtired, and while she had been working out more and eating less because she had found she was a little bigger than the girls she was going up against for jobs, it was by no means to extreme levels. If Kirsten thought she wasn't eating, she maintained, it was because they kept totally different hours, as Kirsten worked nights and Whitney worked days. Personally, she'd said, she felt that there was more to this than just concern. Since arriving in New York, Whitney had clearly been working more than Kirsten ever had, and perhaps that wasn't sitting well. Maybe she was just jealous.

"I am not jealous!" I heard Kirsten say, her voice angry, a few minutes after my mother went downstairs. "Don't you see, she's tricked you. Open your eyes!"

There was more, of course, but I couldn't hear it. And by the time I was called for dinner an hour later, whatever had happened was over, and we were back in default Greene family mode, pretending everything was just fine. And from the outside, I was sure it at least looked that way.

My father designed our house, and at the time it was the most modern one in the neighborhood. Everyone called it "The Glass House," although it really wasn't all glass, only the front. From the outside, you could see our entire downstairs: the living room, split by the huge stone fireplace, the kitchen beyond, and past that the pool in the backyard. You could also see the stairs and part of the second floor—the doorways to my room and to Whitney's, and the landing between them, split by the chimney. The rest was tucked away behind, out of sight. So while it seemed like you were seeing everything, you really weren't. Just bits and pieces that looked like a whole.

The dining room was right at the front of the house, though, so when we ate dinner, we were always in full view. From my seat at the table, I could always see when cars passing slowed down slightly, the drivers glancing in at us for this snapshot, a happy family seated around a hearty meal. But everyone knows looks can be deceiving.

That night, Whitney ate her dinner; it was the first time, but by no means the last, that I noticed this. Kirsten drank too many glasses of wine, and my mother kept saying how wonderful it was we were all together, finally. And repeat, for the next three days.

The morning they left, she sat them both down at the kitchen table and asked them each to make her a promise. She wanted Whitney to take better care of herself, get more sleep, and keep to a healthy diet. Kirsten she asked to keep an eye on Whitney and try to be sympathetic to the pressure she was under living in a new city and working so hard. "Okay?" she said, looking from one of them to the other, then back again.

"Okay," Whitney said. "I promise."

Kirsten, though, just shook her head. "It's not me," she said to my mother, pushing back her chair and standing up. "I warned you. That's all I'm going to say. I told you, and you are choosing not to listen to me. I just want us all to be clear on that."

"Kirsten," my mother said, but she was already gone, walking out to the garage, where my father was putting the suitcases into the car.

"Don't worry," Whitney said, getting up and kissing my mom on the cheek. "Everything's fine."

For a while, it seemed like it was. Whitney kept getting jobs, including a shoot for New York magazine, her biggest yet. Kirsten got a new hostessing gig at a very famous restaurant, and a cable TV commercial. If they weren't getting along, we didn't hear about it—instead of one weekly phone call where they passed the receiver between them, now they each called separately, Kirsten usually in the late morning, Whitney in the evenings. Then, about a week before they were due home for Christmas, we got a call during dinner.

"I'm sorry, what?" my mother said, the phone to her ear as she stood in the doorway that led from the kitchen to the dining room. My dad glanced over at her as she lifted her other hand, putting it over her free ear to hear better. "What did you say?"

"Gracie?" My dad pushed his chair back, getting to his feet. "What is it?"

My mom shook her head. "I don't know," she said, handing over the phone. "I can't…"

"Hello?" my dad said. "Who is this?… Oh… I see… Right… Well, that's a mistake, I'm sure… Hold on, I'll find the right information."