I carried our dance bags up to the room that I shared with Jade, but when I opened the door, everything was dark. I flipped on the light switch. My sister was sitting on her bed with her knees drawn up and her chin resting on top of them.

“Go away,” she mumbled.

“It’s my room, too,” I said. I unslung the bags from my shoulders and dumped them on the floor. Tutu had followed me into our room, and she circled our bags, sniffing for traces of pepperoni, as I started to change into my pajamas.

Jade hid her face against her knees. “Are Mom and Dad mad at me?” she asked in a muffled voice.

I shook my head. “Mom and Dad know how much pressure you’re under,” I said.

Jade lifted her head and said angrily, “I can do Clara, you know.”

I’d never seen Jade like this. My sister was an amazing dancer. There was nothing she couldn’t do, and she had always acted like she knew it. So what was upsetting her now?

“I know you can,” I assured Jade. “Has Mr. Kosloff been giving you a hard time?”

Jade shook her head and buried her face again.

It wasn’t easy trying to find the right next question. I felt as if I was tiptoeing around.

“What are the other dancers like?” I asked. I wondered if any of them were bugging Jade the way Renata bugged me.

“Why are you asking so many questions?” she snapped.

As the music began to replay on her laptop, the notes swirled around us, filling the awkward silence.

“If you want to practice, I’ll go back downstairs,” I finally offered.

“No, do what you want,” Jade mumbled.

Up until now, Jade had practiced every chance she got. Something was really wrong, but I couldn’t figure out what. Maybe the best I could do was to take her mind off her problems for a little while. It seemed strange, though, to be the one trying to help her. She was the one who was always coming to my rescue.

“Want to see your outfit then?” I asked. Unzipping my bag, I took out the big brown envelope with the sketches. Tutu immediately dove inside the bag, and the sides of the bag twitched as she poked about.

Jade hesitated. “You told Luisa that you were the only one who could look at them,” she said.

“Well, Luisa might be my best friend, but she’s lousy at keeping secrets,” I said. “But, hey, if you really don’t want to look…”

Jade smiled weakly. “You know I do,” she said.

I stuck my hands into my bag and retrieved Tutu. A towel had gotten snagged on her claws, and I eased it off. Then I opened the envelope of sketches.

Looking at these designs, I felt as if it were already Christmas. Besides a few people at HDC, we were the first ones to see the party costumes. Jade sat up straight as I excitedly flipped through the sketches.

When I saw the costumes for the mice and the soldiers, I realized that Margie must have misunderstood Mr. Kosloff and given me all the kids’ costumes for Act One instead of just the party outfits. I slid the battle costumes back into the envelope and began to go through the party designs. Mr. Kosloff had made a lot of notes and cross-outs on each page. When I saw Clara’s outfit, I held it up dramatically. “Ta-da!” I announced.

Jade stood up so that she could look at the outfit more closely. It had a fitted lavender top with long sleeves and a skirt with a sheer layer over a full flaring underlayer. We studied the design. “It’s pretty,” I said, “but…it could be better.”

Mr. Kosloff had scribbled notes in the margin beside Jade’s party dress. Jade jabbed her finger at one of the notes. “Lavender isn’t my color,” she said. “I should be wearing light blue. And look at how long those sleeves are. They make this look like an old lady’s dress.”

“Light blue is fine up close,” I said. “But on the stage in a big theater, you have to have a color that will make you stand out.” I studied her complexion. “It should be red.”

“I want light blue,” she said.

I shook my head firmly. “Red.”

“You asked for my opinion,” Jade argued.

“No, I asked you if you wanted to look at the designs,” I countered. “It was just to satisfy your curiosity.”

“I know what color’s best for me,” she snapped as she flopped back down on her bed.

Mr. Kosloff wanted my opinion, not yours, is what I thought to myself, but I just said, “You’re right about the sleeves.” I thought about shortening them, but that didn’t seem to be enough. So I drew the dress without sleeves. “How’s this?” I asked, showing her my revisions.

Jade picked up her earbuds and fiddled with the cord. “Better,” was all she said.

I thought that after making such a fuss about the dress, Jade might be more excited about the new sketch. So I looked at it again. Something still seemed off. “Do you think the dress is too plain?” I asked. “After all, you’re the star of the party.”

“Just do what you want,” she said. “You’re not going to listen to me anyway.”

I tried to control my temper. “Jade,” I said, “what’s bugging you?”

She shook her head and looked away. “Don’t worry about it, Isabelle,” she said. “Mr. Kosloff made some changes to my routine that I’ve got to remember.” She plugged her earbuds into her laptop and then fitted them snugly into her ears. Closing her eyes, she began to listen to the music again. She must have been visualizing her routine, because every now and then she’d move her arm or her wrist.

Jade couldn’t fool me. Whatever was bothering my sister was more than just a few changes to her routine. I had to find out what it was—and try to help her fix it.

I carried the envelope of costume designs downstairs, planning to look at them in the living room. But I bumped into Mom as she was coming out of her sewing room.

“Just the girl I wanted to see,” she said. Pulling me inside, she led me over to a tall white armoire against the far wall of the room. When she opened the doors of the armoire, I stared in amazement. Usually the shelves of the armoire were crammed with fabric and piles of stuff from Mom’s work, like photos and X-rays of old dresses from the Smithsonian. But today the shelves were clean and bare, except for a white wicker sewing basket, a tidy pile of colorful fabric swatches, and the small purple sewing machine that Mom sometimes let me use. She lifted the sewing basket off the shelf and showed me what was inside: spools of thread, a tape measure, a pair of scissors, and a pincushion.

“For you,” Mom announced, waving her hand toward the armoire with a flourish. “I thought you could make this your own and work on your designs in here.”

I knew that space was precious in a room filled with stuff from floor to ceiling. “Mom, really?” I said.

She gave me a little hug. “I know you want to be a dancer, Isabelle,” she said, “but I think you’ve got a talent for design, too. I’d like you to keep developing that when you can.” She pointed me toward the oak desk that had belonged to my grandfather. “I cleared off some space at my desk for you, too,” she added.

As I sat down in the chair in front of the desk, I felt like a queen in her castle.

“You’ll find colored pencils and erasers in the drawer,” Mom said. “Is there anything else you need?”

I shook my head, almost too happy to speak. When I set the envelope on the desk, Mom started to reach for it but pulled her hand back.

“Do you want to see the designs?” I asked.

Mom looked tempted, but then she shook her head. “If I look at them, I’ll wind up making comments,” she said. “And Mr. Kosloff wanted your ideas, not mine.” She bit her lip, as if holding back something else.

“Spill,” I said. “I can see you want to tell me something.”

Mom nodded and smiled. “Just remember one thing,” she said. “An outfit not only has to look good on paper, but it also has to look good and move well when a real person wears it.”

I thought about some of the clothes I had drawn when I was small. “Like a dress that looks slim and neat on paper but would be so tight, you could hardly walk in it?” I asked.

“That’s it,” Mom said. “Don’t stay up too late, Isabelle, okay?” She kissed my forehead and left to get ready for bed.

I kept Mom’s advice in mind as I began to go through the party outfits. Though all of the costumes looked danceable, I had suggestions for how to improve most of them—I couldn’t help it! Sometimes all I did was suggest a new color or pattern. Other times I widened a collar or lengthened a cuff or suggested a thinner belt. The ideas just kept coming.

After I had written my notes and drawn my sketches by the designs for the party outfits, I should have stopped there. But I couldn’t help sneaking a peek at the other designs from the battle scene. The soldiers’ uniforms were colorful enough, but the mice looked like weasels to me.

Since I wasn’t supposed to have seen those designs, I should have just slipped them back into the envelope with the other stuff. But they bothered me. Why would weasels invade a house? I know the mice were supposed to be the villains, but these designs seemed too scary. Mice should look like mice, so I wrote a suggestion that the muzzles be shorter and rounder. I wasn’t sure Mr. Kosloff would understand my note, so I made a sketch, too.

Then I almost erased it, afraid that Mr. Kosloff would get mad at me for doing more than I was supposed to. And had I gone too far in the other direction and made the mice too cute? I got as far as touching the eraser to the paper, but I didn’t use it. When something felt not quite right, I had to do something about it. So I slid the mouse sketch into the envelope with everything else.

Jade was already asleep when I crept upstairs and into our room. Tutu was curled up next to her. As I crawled into my own bed, I glanced at my sister. Helping Mr. Kosloff had been easy. Helping Jade was going to be a lot harder. But I wasn’t going to give up.