All Hester Thursby wanted was a single day to herself, and today was going to be that day — even if it killed her. She left the baby monitor on the nightstand next to her snoring non-husband, Morgan, and slipped out of the house with Waffles on the leash. Okay, maybe she glanced into Kate's bedroom to be sure her three-year-old niece was still alive; maybe she crept up to the queen-size bed where the tiny girl slept within a protective barricade of stuffed animals. And maybe Hester felt a wave of relief when Kate rubbed her nose with a fist and rolled over. Kate had been staying with them since September, and no matter how much Hester wanted to keep the kid from cramping her style, she still hadn't adjusted to worrying about another human being all day and every day. "We're making this up as we go along, kid," she whispered, kissing Kate's forehead.

Outside was quiet and dark in the way only a frigid morning in December could be. Today was Morgan's day to watch Kate — the first free time Hester had had in nearly three months. She took the dog straight to Block 11 in Somerville's Union Square, where she ordered the biggest cup of coffee available and a scone to split with the basset hound. She added cream and seven sugars to the coffee. At the park, she let Waffles off the leash to have at it with the other dogs and then planned her day. Maybe she'd hit the Brattle Theater for that George Romero series, or wander the streets of Cambridge, or drink till she was drunk. Maybe she'd do all three.

"You're off somewhere."

Hester glanced up at Prachi — O'Keefe the greyhound's "mom" — who loomed over her (though even some ten-year-olds loomed over Hester). As always, Prachi, who was a partner in a corporate law firm, looked relaxed, with her cocoa-colored skin and the well-rested eyes of the child free.

"Just daydreaming," Hester said.

"We missed you last night," Prachi said.

Prachi and her partner, Jane, threw an early-winter party each year, one where guests spilled into every room and the air smelled of curry instead of cloves. It was an event Hester looked forward to, but the party hadn't started till eight, which had meant nine, well after Kate's bedtime.

"Finding a babysitter on a Friday in December is next to impossible," Hester said. "Who knew?"

"Darling, you can still hit the town," Prachi said. "It's not like you died. We all love Kate."

"I'm learning how to do this as I go along. Turns out there's no manual on raising someone else's kid."

"Any word from Daphne?"

"Nada," Hester said.

Daphne was Kate's mother and Morgan's twin sister. She was also Hester's best friend. Hester had known her since college, long before Daphne had introduced her to Morgan. Three months earlier, in September, Daphne had skipped town while Hester and Morgan had been out to dinner with Prachi and Jane. The four of them had come home, drunk and ready for a nightcap, only to find Kate asleep with a note beside her. On it, Daphne had written in block letters: Back in an hour. Tops.

They hadn't heard from her since.

Hester wasn't surprised — Daphne had a history of disappearing for long stretches and then showing up unannounced as though she'd gone to the gym for an hour — but Hester still worried about her friend, and the kid thing upped the stakes, to say the least. She didn't have kids of her own, and that was by choice.

She called to Waffles. As usual, the basset had found something far too fragrant to bother coming. "I should see what she got into," she said to Prachi. "I'll catch you tomorrow."

At the house, Hester heard Kate say, "No," her not-so-new favorite word, and she opened the door in time to see a plastic bowl of Cheerios skid across the kitchen floor. Morgan was on the phone, his red morning hair still sticking straight up. He was handsome in a kind way, with freckles that merged into each other and green eyes that matched his sister's. He went to the gym, but without conviction. He mouthed "please" as he handed over a piping-hot bowl of oatmeal. Ever since Kate had moved into the house, Morgan had proven himself to be hapless at childcare. He gave Kate orange soda for breakfast and let her run wild in the park while he yammered on his cell phone. And whenever Hester tried to bring up Daphne, to talk about what was happening to them, he acted like leaving a three-year-old alone in an apartment while you skip town was normal behavior for a parent. But then Morgan and Daphne always watched out for each other, no matter what the behavior. They were twins in every way.

Hester let the leash drop so that Waffles could do the majority of the cereal cleanup, and then lifted Kate from her high chair while the kid shouted, "Kate hate Cheerios!" even though some days she ate only Cheerios. Hester chased her through the living room, around the dining table, into Morgan's office, up the stairs, through each of their bedrooms, and down the stairs, till she finally caught Kate, lifted her up, tickled her, strapped her into the chair, and poured another bowl of cereal, which Kate ate like she hadn't been fed in a week.

"Never," Hester said, as she mussed Kate's curly hair. "I will never understand the logic of being three years old. Not in one million years."

"Not in one million years," Kate aped.

Morgan hung up the phone. "That was the emergency animal hospital in Porter Square."

Though Morgan had his own veterinary practice, once Kate had moved in with them — and her preschool bills had begun showing up — he'd started taking spare shifts whenever he could.

"They need someone last-minute."

Hester smiled at Kate and then waved Morgan to the other side of the apartment. "Are you shitting me?" she whispered.

Morgan smiled in a way that usually got him what he wanted, but all Hester could see was a spot of fury that had taken the place of the day on her own.

"Sorry, Mrs.," he said

A part of her understood, the part that knew they needed the money. But most of her wanted to scream. Plus, she hated it when he called her "Mrs." "You owe me," she said. "Big time."

Morgan kissed her cheek, put his coat on, and whistled for Waffles to come with him. Soon Hester heard him back his truck out of the driveway. "You're stuck with me today, kid," she said, though now Kate was only interested in her stuffed monkey, Monkey, dancing the toy across her lap and saying, "Monkey One Hundred Forty Silly Pants eating bananas," which sounded like "Mokah anhendrd farty sesty pints tang banants." Hester couldn't believe she understood anything the kid said. It was a secret language that only she, Kate, and Monkey spoke. In truth, Hester couldn't believe any of this was happening. But it was.

She sat at the counter and tapped a finger on the granite. The long, unstructured day stretched in front of her. One of the mothers at day care had asked to schedule a playdate only yesterday, and Hester had answered evasively, still unable to commit, still wondering whether Daphne would stroll through the door at any moment expecting things to go back to normal. What was normal, anyway? She pulled up the Brattle Theater schedule on her phone and wondered momentarily if Kate could sit through Night of the Living Dead without getting too scared.

She really was a shit parent.

Her phone rang. She didn't recognize the number with a New Hampshire area code but picked up anyway.

"I heard that you find...