The train was packed with holiday shoppers. Department-store bags with glossy Christmas scenes clogged the aisles.

An old man carrying a small leather suitcase got on at Monroe and squeezed through the crowd to the back of the train, where someone had just stood up. The old man, who smelled faintly of pipe tobacco and wine, had a white mustache and thick white hair under his cap and wore an ascot tie. He moved to sit down but stumbled as the train jerked forward, cracking his knee against the plastic seat. A woman across the aisle gave him a withering look.

“I have a suitcase, dear, so it’s harder,” he said. He looked at the woman he’d sat next to, who was staring out the window. “I parted the waters,” he whispered out of the side of his mouth. She didn’t respond.

Two children boarded at the next stop and wove past the passengers’ legs to the back of the train.

“Who would wait that long to see Santa?” said the girl, who was 12 or 13 and wearing eyeshadow and lipstick. “Not I.”

The boy’s eyes were red, and he kept trying to see through the crowd to his parents, who were trapped near the doors.

The old man caught the boy’s eye and winked. “I bet you waited, didn’t you?”

“No, he didn’t,” said the girl. “Scaredy-cat got scared by the fireworks.”

The boy clapped his mittened hands over his ears and stared solemnly at the old man.

The girl looked at her hair in the window of the conductor’s compartment and said, “Ugh.” Then she reached over and snatched off her brother’s hat. His hair was flat on top and stuck out around the ears. “Hat head, hat head,” she said, and threw the cap at his feet.

He picked it up silently and kept staring at the old man.

“I’ll be Santa,” the old man said. “Pretend I’m Santa.” He puffed out his belly and adopted a mock deep voice. “And what would you like for Christmas, young man?”

“He wants Nintendo Game Boy and Power Ranger,” his sister said.

“Let the boy tell,” said the old man, still in the mock voice.

“You don’t have no beard,” the boy said.

“I used to have one,” the old man said. “I have a mustache. How’s that? Is that good enough?”

The boy shook his head from side to side.

“I suppose I lose my Santa license,” the old man said, smiling.

The train stopped suddenly, pitching the passengers forward. The boy gaped open-mouthed at them.

“It’s fun riding the train, isn’t it?” the old man said. “Can you ride without holding on to the rail? I bet you can.”

The boy let go of the rail, but he stumbled into his sister as soon as the train started moving.

“Don’t touch me, doofus,” she said.

“What’s really fun is if you give yourself lots of room,” the old man said, leaning forward. “Pretend you’re riding a surfboard. Spread your legs and stand sideways. Then if you start falling you can stop yourself.”

The boy and the girl both tried this time. The train screeched around a curve, and the boy fell on his rump. The girl kept her balance, but she was holding on to the bar behind her back.

“She’s using the wall to lean on,” the old man said. “She’s cheating.”

“Am not.”

“Give it another try,” he told the boy.

“You try,” said the girl. “You want everyone else to try. I bet you can’t do it.”

“Do you know everything, young lady?” he said.

“I don’t know why you’re wearing that stupid tie.”

“Right there. You don’t even know what this is called.”

“Like I care.”

“It’s an ascot, Miss Smarty-pants.”

“It’s an ass.” She giggled and covered her mouth. “Miss Smarty-ass.”

The children got off with their parents at the next stop. “Bye ass,” the girl called on her way out the door.

The boy trailed behind as the family walked along the platform in the light snow. He kept springing into surfing position, throwing his arms out for balance.

“And a Merry Christmas to you too,” the old man said to the woman beside him.

She got up and moved to another seat.

“Oh, piss off,” he said. By the next stop he’d fallen asleep.