Every year that Thomas could remember, Aunt Sadie decorated the outside of the Morans’ house with Christmas lights in early December.

“What’s the point of decorating an apartment?” she’d say to Helen as she dragged the stepladder out of the garage. “No one can see it.”

Thomas and Helen would watch her progress through the living room window. Mr. Moran couldn’t look because Aunt Sadie was sloppy about the lights. In a very un–Aunt Sadie–like way, she draped them wherever it was handy—over the drainpipe, on the rim of the roof, down to the yew bushes outside the living room. Every year a different path to lighting up the darkness. She did it like this because that was how their father had done it. And Aunt Sadie wanted to preserve the custom for her and Helen—as well as teach it to Thomas.

“Just think, Brian,” Aunt Sadie had told his father. “That’s how Santa knows where to bring Thomas’s presents. ‘Thomas Moran? Oh, that’s right. The sloppy house.’ ”

“No,” Helen had corrected her sister. “The house that looks like the night sky. On a clear night. Under a full moon.”

The lights were always the same…little white icicles that shone like crystals against the snow.

Now it was Christmas Eve and Mr. Moran had handed them over to Aunt Sadie—tested and untangled. She went outside and stood there looking up, big loops of electrical cord dangling over her arms. The last thing on their mind this year in early December had been decorating the house with lights, but Thomas knew Aunt Sadie believed in traditions. He watched his aunt from his spot by the living room window. She wasn’t wearing her Santa hat; she wasn’t even wearing gloves.

Finally, he opened the side door for her to come back inside.

“Sorry, Duck,” she said. “I thought it would make us feel better, but it just doesn’t seem right.”

Thomas nodded. He sat down on the landing. Aunt Sadie sat down, too, sliding her back against the door until her bottom was in the puddle her boots made, lights on the floor all around her.

She let her head drop. “I miss my sister,” she said. And she began to cry.

From the ache in his stomach, Thomas knew that Dave was crying, too, his head tucked under his wings. Thomas thought about this as he crawled toward his aunt, popping little white lights under the pressure of his knees.

He sat in her lap in the darkness until Thomas’s father came up from his office and flipped on the light in the landing. It was so bright, Thomas was blinded for a moment.

No one spoke.

Mr. Moran got a tissue box and the broom from the kitchen. Placing her hands around Thomas’s waist, Aunt Sadie moved him off her lap. She went into the kitchen and took her overnight bag and a package of extra lights that hadn’t been opened from the table.

“I’ll be back,” she said, and went upstairs.

But she didn’t come back. Not right away. Thomas and his father had their dinner. When they were washing up, Aunt Sadie stood in the doorway.

“I’m going to church…to light a candle for my sister.”

Thomas and his father hadn’t been to church since Helen went away.

On Christmas Eve, they’d always made popcorn and drank mulled cider. They put Duraflame logs in the fireplace and sat with only the Christmas lights and the firelight.

This year, the fireplace was dark. There was no tree. There were no lights.

“Do you…want to watch a Christmas special?” his father asked Thomas.

“I’m tired.” Thomas was already climbing the steps to his room.

“Here.” His father bent to one of the unpacked Christmas boxes, opened it, and handed Thomas a book his mother read to them every year.

“I’ll come up in a little while and we’ll read.”

The book was titled The Christmas Promise. He remembered it well. It was about a bad time in history when a man had to leave his daughter behind to search for work. He promised to return by Christmas, and though it looked like he wouldn’t keep his promise, he did return. On Christmas Day.

As Thomas walked up the stairs, he realized he did not believe in promises. They weren’t observable. Entering his dark room, Thomas climbed onto his bed and set the book on the bedside table. As he lay down, pressing his face into the pillow, something poked his stomach. It wasn’t Dave. This was from the outside, a sharpish object, wrapped in a piece of lined paper and tied at either end with a string.

A present?

Thomas sat up and undid the string. The remote control for the outside Christmas lights tumbled into his lap. He pressed the power button; at the edge of his vision, a soft light glowed. He saw that the glow came from beneath his mattress. Like he was floating on a cloud of light.

UnderLand.

Removing the sweater boxes, Thomas scooted underneath. Between the mattress and the metal frame Aunt Sadie had placed the string of white Christmas lights. She must have taken off the mattress and poked each strand through, because the little white icicles dangled above him like caterpillars.

Thomas shimmied over to his usual place. Inside Helen’s coat, Aunt Sadie had placed a book, a big blocky book that smelled like old pages.

“Folk and Fairy Tales the World Over,” Thomas whispered to himself as he read the title. He opened the book to the first page. On it, his aunt had written:

For Thomas, who will write us a happy ending.