Sylvia liked wandering the house at night – it was her own secret life that no one else knew about. It made her powerful, as if she could see their secrets too. She wandered into Julia's room, no chance of disturbing her sleep. You could have pushed her out of bed onto the floor and jumped on Julia and she wouldn't have woken up. You could have put a pillow over her face and suffocated her and she would have known nothing about it. She was drenched in sweat, you couldn't even put your hand near her she was so hot, and you could hear her breath being squeezed in and out of her lungs.

Sylvia suddenly realized that Amelia's bed was empty. Where was she? Did she have a secret, wandering nightlife too? Not Amelia – she didn't have the initiative (Sylvia's new word) for a secret life. Was she sleeping with Olivia? Sylvia hurried to Olivia's room and found Olivia was gone from her bed too. Half of them missing – not taken by aliens, surely? If aliens existed – and Sylvia suspected they did – God must have created them, because God created everything, didn't he? Or had he not actually created everything, only the matter in our own galaxy? And if there were other worlds then they must have been created by other gods, alien gods. Was that a blasphemous thought?

There wasn't really anyone she could consult with over these knotty theological problems. She wasn't allowed to go to church, Daddy didn't believe in God (or aliens) and the religious education teacher at school had told her that she had to stop "bothering" her so much. Imagine Jesus saying, "Go away, don't bother me so much." God would probably send the religious education teacher straight to hell. It was very difficult when you had been brought up by an atheist who was a mathematical pig and a mother who couldn't care less and then you heard the voice of God. There was so much she didn't know – but then look at Joan of Arc: she was an ignorant French peasant and she'd managed, and Sylvia was neither ignorant nor a peasant. After God spoke to her Sylvia began to read the Bible, at night under the bedcovers by the light of her trusty Eveready torch. The Bible bore no relation to Sylvia's life in any way. That alone made it very attractive.

Sylvia tried to recollect bedtime the previous evening but she could only form a hazy memory. She had felt sick with the heat and the sun and had gone to bed before anyone else. The minute her back was turned had Mummy allowed Amelia and Olivia to sleep in the tent? Would she? Mummy had been so adamant all summer (for no good reason whatsoever) that they couldn't sleep outside.

Sylvia crept downstairs, avoiding the two steps that creaked. The back door was unlocked so that anyone could have walked right in and done the aforementioned murdering in the beds. It was unlocked, of course, because Amelia and Olivia were sleeping in the tent. It would be dawn soon, she could already hear a solitary bird greeting the morning. The grass on the lawn was wet. Where did all the dew come from when it was so hot and dry during the day? She must look it up in a book. She trod carefully across the lawn in case she stood on the soft, sluggy body of some other nocturnal creature leading its own secret life.

She lifted the flap of the tent. Yes, they were both there! What a cheek. Why should Amelia get the prize of sleeping all night in the tent, and not just sleeping in the tent but sleeping with Olivia and Rascal? It wasn't fair. Sylvia was the eldest, she should be in the tent. Rascal climbed out from beside Olivia and wagged his tail and licked Sylvia's nose.

They were both sleeping on their backs, dead to the world, like corpses. Sylvia shook Amelia's feet but she wouldn't wake up. She squeezed herself into the tent, between the two of them. It was incredibly hot in the tent – it was probably hot enough to kill them. The hottest place on earth – was it the Atacama Desert? Death Valley in America? Somewhere in Mongolia? They weren't dead, were they? She pinched Amelia's nose and Amelia muttered something and rolled over. She should wake Olivia up and take her out of this hothouse. The Black Hole of Calcutta, the people who died in there died from the heat, not the lack of air – a common misconception. "Misconception" was an excellent word. The afterthought - there was a misconception if ever there was one. Ha. Their mother really should stop breeding, it was very base. Perhaps she was a secret Catholic. That would be wonderful, then they could have long, clandestine conversations about mystery and ritual and the Virgin Mary. Neither the Virgin Mary nor Jesus had spoken to Sylvia. She didn't think that Jesus actually spoke to people. Joan of Arc was another matter -Joan of Arc was downright chatty.

Sylvia rubbed Olivia's earlobe because Rosemary had once said that was how they roused sleeping patients when she was a nurse. Olivia stirred and then fell helplessly back into sleep. Sylvia whispered her name and she struggled to open her eyes. She was bewildered with sleep, but when Sylvia whispered, "Get up, come on," she followed Sylvia out of the tent, carrying her little pink rabbit slippers in her hand. Sylvia said, "Don't bother about your slippers, feel how wet the grass is between your toes," but Olivia shook her head and put her slippers on. Sylvia said, "You have to learn to be rebellious. You mustn't do everything Mummy and Daddy tell you. Especially Daddy." And then she added, "Except me, you should obey me." She wanted to say, "Because I have heard the word of God," but Olivia wouldn't understand. Nobody understood, except for God, of course, and Joan of Arc.

The first time God spoke to her she was sitting on the sidelines during a hockey match. Sylvia, an inventive right wing, had been sent off for hitting her opponent around the ankles with her stick (the whole point to win, surely?) and she was sulking furiously when a voice close by said, "Sylvia," but when she looked round there was no one there, only a girl called Sandra Lees who spoke with a squeaky Cambridge accent, so unless Sandra Lees was practicing ventriloquism or had changed into a man, it couldn't have been her. Sylvia decided she had imagined it, but then the voice said her name again – a deep, mellifluous voice, a voice that bathed her in warmth, and this time Sylvia whispered, very quietly on account of the proximity of Sandra Lees, "Yes?" and the voice said, "Sylvia, you have been chosen," and Sylvia said, "Are you God?" and the voice said, "Yes." You couldn't get a much clearer message than that, could you? And sometimes she felt so transformed by the holy light that she simply swooned away. She loved it when that happened, loved the feeling of losing control, of not being responsible for her body or her mind. Once (perhaps more than once), she had swooned in Daddy's study – blacking out and crumpling to the floor like a tortured saint. Daddy threw a glass of water in her face and told her to pull herself together.

Sylvia whispered to an almost sleepwalking Olivia, "Come on, let's go and play a game," and Olivia said, "No," and sounded whiny and not at all like her usual pliant self. "S'night," she objected, and Sylvia said, "So what?" and took her hand and they were halfway across the lawn when Olivia exclaimed, "Blue Mouse!" and Sylvia said, "Hurry up and fetch him then," and Olivia crawled back into the tent and reemerged, clutching Blue Mouse by one arm, Rascal bouncing happily at her heels.

Joan of Arc had spoken to her when she was sitting high up in the branches of Mrs. Rain's beech tree. Joan of Arc talked into her ear, for all the world as if she were sitting companionably on the branch next to her. The funny thing was that after these conversations Sylvia could never really remember anything that Joan of Arc had actually said and she had the impression that she hadn't spoken at all, she had sung, like a great bird perched in the tree.