Julia emerged from beneath the hydrangeas looking querulous with heat. How was Rosemary ever going to turn them back into English schoolchildren when the new term began? Their open-air life had transformed them into gypsies, their skin brown and scratched, their sun-scorched hair thick and tangled, and they seemed to be permanently filthy, no matter how many baths they took. A drowsy Olivia stood at the opening of the tent and Rosemary's heart gave a little twitch. Olivia's face was grubby and her bleached plaits were askew and looked as if they had dead flowers entwined in them. She was whispering a secret into Blue Mouse's ear. Olivia was her only beautiful child. Julia, with her dark curls and snub nose, was pretty but her character wasn't, Sylvia – poor Sylvia, what could you say? And Amelia was somehow… bland, but Olivia, Olivia was spun from light. It seemed impossible that she was Victor's child, although, unfortunately, there was no doubting the fact. Olivia was the only one she loved, although God knows she tried her best with the others. Everything was from duty, nothing from love. Duty killed you in the end.

It was very wrong, it was as if the love she should have had for the others had been siphoned off and given to Olivia instead, so that she loved her youngest child with a ferocity that didn't always seem natural. Sometimes she wanted to eat Olivia, to bite into a tender forearm or a soft calf muscle, even to devour her 'whole like a snake and take her back inside her where she would be safe. She was a terrible mother, there was no doubt about it, but she didn't even have the strength to feel guilty. Olivia caught sight of her and waved.

Their appetites were listless at teatime and they picked at the unseasonable lamb hot pot that Rosemary had spent too much time making. Victor emerged, blinking in the daylight like a cave dweller, and ate everything in front of him and then asked for more, and Rosemary wondered what he would look like when he was dead. She watched him eating, the fork traveling up and down to his lips with robotic rhythm, his huge hands, like paddles, wrapped around the cutlery. He had farmer's hands, it was one of the things she had first noticed about him. A mathematician should have slender, elegant hands. She should have known from his hands. She felt sick and crampy. Maybe she would lose the baby. What a relief that would be.

Rosemary rose from the table abruptly and announced bedtime. Normally there would be protests but Julia's breathing was labored and her eyes were red from too much sun and grass – she had all kinds of summer allergies – and Sylvia seemed to be in the grip of some form of sunstroke, she was sick and weepy and said her head hurt, although that didn't stop her from being hysterical when Rosemary told her to go to bed early.

Almost every night that summer the eldest three had asked if they could sleep outside in the tent, and every night Rosemary said no on the principle that it was bad enough they looked like gypsies without living like them, and it didn't matter if gypsies lived in caravans – as Sylvia was at pains to point out – Rosemary was trying her best to retain good government in this family, against all the odds and without any help from a husband, for whom the quotidian demands of meals and housework and child care were meaningless and who had only married her in order to have someone who would look after him and it made her feel worse when Amelia said, "Are you alright, Mummy?" because Amelia was the most neglected of all of them. Which is why Rosemary sighed, took two paracetamol and a sleeping tablet – which was probably a lethal cocktail for the baby inside her – and said to her most forgotten child, If you want you can sleep in the tent with Olivia tonight.

The dewy grass and canvas smell of the tent was a thrilling thing to wake up to – better certainly than Julia's breath, which always seemed to grow sour in the night. Olivia's own indefinable scent was just detectable. Amelia kept her eyes closed against the light. The sun already felt high in the sky and she waited for Olivia to wake and climb under the old eiderdown that was making do as a sleeping bag, but it was Rascal rather than Olivia who finally roused her by licking her face.

There was no sign of Olivia, only an empty shell of covers as if she'd been winkled out of them, and Amelia felt disappointed that Olivia had got up without waking her. She walked barefoot across the dew-wet grass, Rascal trotting at her heels, and tried the back door of the house, which turned out to be locked – apparently her mother hadn't thought to give Amelia a key. What kind of a parent locks her own children out of their home?

It was quiet and felt very early but Amelia had no idea what time it was. She wondered if Olivia had got into the house somehow because there was no sign of her in the garden. She called her name and was startled by the tremor in her voice. She hadn't realized she was worried until she heard it. She knocked on the back door for a long time but there was no answer, so she ran along the path at the side of the house – the little wicket gate was open, giving Amelia more cause for alarm – and into the street, shouting, "Olivia!" more forcefully now. Rascal, sensing entertainment, began to bark.

The street was empty apart from a man getting into his car. He gave Amelia a curious look. She was barefoot and dressed in Sylvia's hand-me-down pajamas and supposed she did look odd but she hardly cared. She ran to the front door and rang the bell, keeping her finger on the buzzer until her father, of all people, yanked the door open. He had obviously been roused from sleep – his face looked as rumpled as his pajamas, his mad-professor hair sticking out at all angles from his head as he stared fiercely at her as if he had no idea who she was. When he recognized her as one of his own he was even more puzzled.

"Olivia," she said, and this time her voice came out as a whisper.

In the afternoon, a bolt of lightning cracked the flat skies above Cambridge, signaling the end of the heat wave. By that time, the tent in the back garden had become the center of a circle that had grown wider and wider as the day progressed, pulling more and more people inside it – first the Lands themselves, roaming the streets, scrambling through undergrowth and hedges, yelling Olivia's name until they were hoarse. By then the police had joined the search and neighbors were checking gardens and sheds and cellars. The circle rippled outward to include the police divers fishing the river and the complete strangers "who volunteered to comb meadow and fen. Police helicopters flew low over outlying villages and countryside as far as the county borders, truck drivers were alerted to keep an eye out on the motorway, and the army was brought in to search the fens, but none of them – from Amelia screaming herself sick in the back garden to the Territorial Army recruits on their hands and knees in the rain on Midsummer Common – could find a single trace of Olivia, not a hair or a flake of skin, not a pink rabbit slipper nor a blue mouse.