In a moment DeAnne was holding a dripping Betsy out in front of her, taking her around the car to her seat, where she had already spread a cloth diaper to protect the leather.

Robbie, the four- year-old, was awake now, too, holding out his arm. He had been sitting in the middle, right next to Betsy, and there was a streak of vomit on his sleeve. "Wasn't that sweet of your sister, to share with you," said Step. He wiped down Robbie's sleeve. "There you go, Road Bug."

"It stinks."

"I'm not surprised," said Step: "Bear it proudly, like a wound acquired in battle."

"Was that a joke, Daddy?" said Robbie.

"It was wit," said Step. Robbie was trying to learn how to tell jokes. Step had given him the funny-once lecture recently, so Robbie wasn't telling the same joke over and over again, but the different kinds of humor still baffled him and he was trying to sort them out. If Stevie's experience was a fair sample, it would take years.

DeAnne spoke to Robbie from the front seat. "We'll change your shirt as soon as your father has finished wiping up Betsy's booster seat."

Step wasn't having much success cleaning down inside the buckle of Betsy's seat belt. "The only way our seat belts will ever match again," he said, "is if Betsy contrives to throw up on all the rest of them."

"Move her around in the car and maybe she'll have it all covered by the time we get to North Carolina," said Stevie.

"She doesn't throw up that often," said DeAnne.

"It was a joke, Mom," said Stevie.

"No, it was wit," said Robbie.

So he was getting it.

The baby wipes were no match for Betsy's prodigious output. They ran out long before the seat was clean enough for occupancy.

"When they hear you're pregnant for the fourth time," said Step, "I think Johnson & Johnson's stock will go up ten points."

"There's more wipes in the big grey bag in the back," said DeAnne. "Make sure you buy the stock before you announce it."