Two hours later, Alison sat curled up in the passenger seat of Barbara's car, lulled by the hum of the engine and the flicker of motorway lights going past. She'd taken the largest dose of oxycodone she dared, and it had driven the last of the pain away, leaving her as hollow and empty inside as the high vault of the church they'd visited. There, she'd told a weary-looking young priest a vague story and received a cheap St Michael medal, which she'd hung round Barbara's neck on the theory that Barbara needed protection most. The priest had blessed them both with chrism as well, and now the car was full of a sweet balsam scent that reminded Alison pleasantly of her long-ago confirmation. She wished there were something that could give Barbara the same sort of comfort, false though it might be. You didn't have to be psychic to see the apprehension written all over Barbara's face, even in profile.

"All right if I use your phone again?" she asked.

Barbara said that it was, and Alison picked the phone up and dialled Helen's number for the fifth time since they'd left the church. She was desperate to reach Helen, not so much because she thought Helen would be able to tell her how to deal with John Collier's spirit, but because she wanted so badly to talk to someone who understood. Barbara was trying hard, but her belief in such things was new and fragile, not the bone-deep knowledge of someone who'd lived an entire life at the overlapping edge of two worlds.

"No answer?"

Alison shook her head, listening to the endless ringing. Worry for Helen was beginning to creep in round the edges of her worry about their situation in general. Helen was old and hard of hearing, but by that token, she should be safely ensconced in her chair at half past six on a Saturday evening, with her dogs at her feet and the phone close to hand. If something had happened - no, she'd know if something had, she was certain of it.

"Please be there," she whispered. "Please be all right."

Barbara threw a swift glance in her direction. "Whom are you trying to reach, or shouldn't I ask?"

"Her name is Helen - she was a friend of my aunt's, I've known her since I was a little girl." As she said it, she had a sudden, vivid memory of sitting at the kitchen table between Vi and Helen, watching as Helen's eyes turned back to show blank, dead whites, as the pencil in her limp hand scrawled across a sheet of paper of its own accord, scratching out a mad mixture of words and names and numbers. She'd screamed and cried until Vi had blown out the candles and shaken Helen back to consciousness, and for weeks afterward, she'd refused to do any work at school, terrified that something would take over her body as soon as she picked up a pencil and force her to write what it wanted to say.

"Helen sees things," she added. "The way I do."

"Can she help us then, do you think?"

Alison looked out the rain-spattered window at the dark landscape rolling past, bringing her ever closer to the inevitable confrontation.

"No," she said at last. "I've got to do it on my own."

"Not all on your own," Barbara said. "I'll be there too." Her voice was unsteady but resolute, and Alison felt a rush of warmth toward her. When she was waiting in Robert's office to meet Barbara for the first time, she'd asked him what Barbara was like, and he'd grinned and said that Barbara was bossy, stubborn and thought she was always right, but at the end of the day, there was no one better to have on your side. She was beginning to see what he'd meant.

"You've got a lot of bottle, Barbara Anne," she said sleepily.

She'd said it without thinking, not really expecting any sort of response, and so it came as a shock when Barbara jerked in her seat, slewing the wheel to the left and all but running off the carriageway. Someone's horn blew; a small white car dodged into another lane to avoid them. Alison had a blurry impression of guard rails and shadowy trees, tall and unyielding, but before she could do more than think Oh God, we're going to crash, Barbara got control, downshifted, and came to a rough but serviceable stop at the outside edge of the hard shoulder, where they sat with the windscreen wipers still going and the lights pointing askew at a clump of leafless sycamores that could have killed them.

Barbara shut the engine off and turned on Alison, wild-eyed and nearly panting. "You can't know that. I haven't - you can't."

"Know what? God, what's the matter? All I said was -"

"You said Barbara Anne, it's my full name, but I know I never ..." Her eyes narrowed. "Have you been going through my things behind my back?"

"No," Alison said in righteous indignation, before remembering that she had, in fact, done just that the night Barbara had stayed at her house. But she'd only had a cursory glance at the contents of Barbara's handbag; she hadn't thumbed through her credit cards or inspected her driving licence, and she certainly hadn't done the little she had done with the intent to harm.

Barbara closed her eyes, struggling to get hold of herself. "It's only my brother -- well, he would call me Barbara Anne to tease me. When I was really young I thought it was brilliant that there was a song with my name in it, and then by the time I was eleven or twelve it had become the most embarrassing thing in the world, and so of course Paul, who was a wonderful brother, but also a teenage boy, would go round the house singing it because he knew it got up my nose. My mother made him stop, so he switched to just saying Barbara Anne whenever he got the chance. I never thought I would miss it, but after he died, I did." She rubbed her forehead as if it ached. "I hadn't heard anyone say it like that for years until --"

"I didn't know," Alison said. "I swear it. I know what you're going to say, that I could have seen your full name on a letter or something in your house, or looked it up when we were doing all that research, and I suppose I could have, but I didn't. It just sounded right, so I said it. You don't have to believe me."

"I do believe you," Barbara said. "It isn't logical, but what the hell has been over the last few days?" She laughed, shakily. "We've got to get off the shoulder before someone comes along and hits us. We're not very far from home. We'll be there in less than an hour, and then we can go to ... oh ..."

"Don't think about it until you have to," advised Alison.

Rather than answer, Barbara started the car, let out the clutch and promptly stalled the engine. "Oh God. No, it's okay. It's all right." She waved off Alison's concern and tried again, and in a few seconds they got up to speed and rejoined the flow of traffic. Wind blew the ever-present rain hard against the windows, and doing her best to take her own suggestion, Alison curled up in her seat again and let herself drift away for a bit, which was easy to do with the oxycodone still working its magic inside her. She was dimly aware of time passing, and the car slowing and stopping under bright lights and then starting again, but not much else registered until Barbara shook her by the shoulder.

"Alison."

"Mmmhh."

"We're here."

She let her head roll to the side and opened bleary eyes, and Barbara's house stared back at her from all its windows, somehow managing to look like a forbidding hulk despite its tall, narrow build. Waves of malevolence and ill will rolled out of it toward her; the spirit inside knew she was there, and didn't like it. There were no words, but the message was clear: Go away.

"He's still in there," she said.

"I know it," said Barbara, and Alison glanced over to see that she'd gone deathly pale, as if she were about to faint or be sick or both. She'd pulled the elastic out of her hair, and it hung round her face in untidy dark waves, making her look both softer and younger. Paul would have recognised her straightaway as his little sister, Alison thought.

"Can you hear him?" she asked.

"No. But I can feel him - it - something." Her chin quivered, and for a moment her expression was so vulnerable that Alison wanted to reach over and hug her. "It's inside my head."

Alison nodded. "Mine too."

"I keep thinking that this must be what it's like to be schizophrenic," Barbara said miserably. "I've studied so many patients with that diagnosis, and I never realised how real it must have seemed to them, how frightened they must have been. I kept telling myself that they were people, but really I thought of them as specimens, like lab rats, with interesting conditions that I could publish papers on. It was horrible of me."

"You didn't know," Alison said. "Now you do."

Barbara bit her lip and looked at the house. "We've got to go in, haven't we?"

"You can wait here," Alison said. "It might be safer if you did."

"I said I wouldn't leave you on your own, and I won't," Barbara said in a tone that was closed to argument, and both of them got out of the car without another word.

The sensation of hate and malice got stronger as they got nearer the house, and as they approached the front door, Alison realised she was walking with her head down, leaning forward as if it were a tangible thing she had to push through. Barbara unlocked the door and opened it, revealing nothing but pitch blackness and releasing a wave of frigid air and a stench that made them both choke. It was like opening the door to a cold store full of rotting meat, Alison thought, holding her sleeve over her face in a futile attempt to block some of it out. Very faintly, she caught a hint of balsam, and remembering the holy oil still on her forehead from the priest's blessing, she swiped her fingers across it and then under her nose. Maybe it was sacrilegious, but if there really were a God, she thought He would give her a pass on this one.

Barbara had followed Alison's lead with the oil, and now, holding her breath, she leant in through the doorway, reached for an unseen light switch, and snapped it down, then up, then down again. Nothing happened.

"There's no point to checking the mains, I assume," she said as she drew back.

"Not likely, no," said Alison.

Barbara's mouth firmed into a grim line of determination. "Well, we won't have to go crashing through the dark, anyway," she said, and reaching into her pocket, produced a pair of small electric torches in black plastic casings. She handed one to Alison and switched the other one on, splashing a pool of light onto the door mat.

"I bought them when I was paying for the petrol," she said, seeing Alison's surprise. "I hated it in the graveyard last night. I didn't want to be caught out that way again."

Armed with the torches, they went inside, Barbara automatically pulling the door shut behind her, and stopped in the entrance hall. The atmosphere inside the house had definitely worsened whilst they'd been away, with the trapped spirit exerting whatever influence it could over its surroundings. A faint, frosty white mist drifted all round them and glimmered in the torch beams like dust in a shaft of sunlight. Both of them were already shivering, Barbara harder than Alison, as if the chill from Thursday night had been lurking somewhere deep in her body all this time, waiting for its chance to emerge. The room was quiet except for a small, rapid clicking noise; Alison puzzled over it for a moment, trying to work out what it was, and suddenly realised it was Barbara's teeth chattering. They weren't going to be able to stay too long.

"Come on," she said. "It must be below freezing, or close to it. We've got to keep going to stay warm."

Barbara swung her torch beam round abruptly, as if chasing some fast-moving object. The light flashed across walls and stairs and furniture, but revealed nothing. "I thought I saw something moving." Her voice was a dry whisper. "A shadow -- it's gone now. Upstairs, I think."

"Stay close," Alison said. "He's here."

"Where?" Barbara crowded against her, shoulder to shoulder, and Alison felt her trembling through the double thickness of coats. At the same time, she felt a surge in the powerful emotions that surrounded them, and without stopping to consider, put her hand over Barbara's mouth.

"Sshh. Keep quiet." She concentrated hard, working out what was happening, and identified pleasure and satisfaction among the other, uglier feelings that made up John Collier's personality. Oh, he was a vain one, this man. He'd enjoyed having his neighbours frightened of him when he was alive. He'd wanted to be acknowledged as a witch; he'd been terribly pleased when he was. And --

"He likes you talking," she said to Barbara. "He wants you to notice him. Don't say another word, whatever happens, understand?"

Barbara's eyes were wide and dark and her lips were cold under Alison's fingers; she nodded, and Alison let go, knowing by now that she could be trusted to keep a promise. Leaning hard against the force that wanted to hold her back, she started climbing the stairs with Barbara right beside her, looking for its source. She hadn't been past the ground floor on her previous visit, and when they reached the landing at the top of the stairs, she hesitated, not certain where to go next.

"I'm going to look behind some doors, all right?" she said to Barbara, who made a small gesture of assent and tightened her grip on her torch. Alison took two steps, polished floorboards creaking under her shoes, and pushed open the first door on her right to reveal a spare room that had been converted into an office, with a wall of bookshelves, a small sofa, and a desk that looked as if ten years' worth of paperwork had exploded on it. She shut that door and tried the next one, in which a massive claw-footed bath occupied most of the space. Beyond that was another spare room, this one set up to receive guests; then an odd, poky little room with nothing in it but a ladder that must lead to the loft. At the very end of the corridor were Barbara's bedroom and ensuite bathroom, and they both turned away from that door, gagging; the smell, which they'd begun to get used to, was overwhelmingly strong there.

"No," Alison said, seeing the enquiry in Barbara's eyes. "He isn't in there now, but he has been. He's been there a lot."

In the torchlight, the look on Barbara's face was one of horror bordering on hysteria, and Alison didn't blame her one bit. More than anyplace else in the house, this room showed clear signs of being well used, with the flowered duvet thrown back, jewellery scattered across the bureau top, a pair of shoes kicked under a chair, and an empty glass and stack of books on the bedside table. Barbara owned the whole house, but she lived in this room, and in the untidy little office at the head of the stairs. The thought of an evil spirit choosing to spend its time here was repulsive, a violation.

"We'll make it all right," she promised. "I don't know how, but after all this is sorted, we'll find a way for you to feel safe here again."

Barbara drew a long, shuddering breath, then visibly composed herself and pointed at the floor. Downstairs?

"Has to be," Alison said. "Are you all right to keep going?"

Barbara tucked her torch under one arm and rubbed her hands together. I'm cold.

"So am I. Just a few more minutes, and then if he hasn't shown himself, we'll leave and come back, okay?"

Okay, Barbara said with a curled thumb and index finger. Her hand was shaking almost too hard to make the gesture, and Alison mentally revised "a few more minutes" to "three or four, if that many." She didn't think she could hold out much longer herself; she wasn't hurting from the cold, thanks to the painkillers still circulating in her system, but her feet felt like blocks of marble inside her trainers, and that meant frostbite couldn't be too far away. She gave Barbara a gentle nudge to get her moving, and together they went down the stairs again, through the lounge and dining room and kitchen, shivering and coughing, but finding nothing.

At last they reached the glass-walled conservatory, and as Alison stepped in, she saw, finally, the spirit of John Collier.