They scuttled along the landing and turned into the kids’ corridor, as Cat had come to think of it. Ellie’s room was the second on the right and Cat was enchanted by it. The colours were different tones of lavender and cream, everything blending like a Pantone chart. Watercolours were pinned all over the walls; some landscapes, some seascapes and some of buildings and cities Cat didn’t recognise. Oddly for the room of a teenage girl, there was no mirror on display for Cat to check whether her hostess had a reflection. But at the heart of the room, impossible to avoid, was a large oil painting of a woman. She had a mild and pensive face, fine featured with large blue eyes and a sweep of honey-blonde hair. ‘She’s lovely,’ Cat said.

‘Yes. I wish I looked like her.’

Cat couldn’t help recalling what she’d learned from her reading about vampire ‘families’. They were often loose-knit groups who had chosen to live together over the centuries because they were less visible in a family group. So Margaret Tilney wasn’t necessarily the biological mother of any of the children. Given that she had a separate bedroom from her husband, they may not have been married. Perhaps she wasn’t even his lover; perhaps that was the bone of contention that had led to her imprisonment.

The major flaw in this imaginative view of the Tilneys, which Cat appeared to have mislaid in all her imaginings, was that vampire families had to keep moving because eventually their neighbours and colleagues noticed that nobody in the family seemed to age at the normal rate. Every dozen years or so, they had to disappear and start again. But the Tilneys had been in one place for a very long time and although the men retired from public life at a relatively youthful age, it would still have been hard to fool the whole of the Scottish Borders indefinitely. But no young woman has ever allowed reality to stand in the way of her romantic fantasies, and in this respect, Cat was no exception to the rule.

‘You’re beautiful too, Ellie. Just in a different way.’ Cat put her arm round Ellie’s shoulders and squeezed. ‘And now I can picture what she looked like, why don’t you show me her room so I have her really fixed in my mind’s eye.’

Ellie let herself be steered out of the room and down the gallery. They turned into the middle corridor and passed the General’s room. Ellie paused at the double doors and Cat feared she’d have to make the unthinkable bad-guest-move and open them herself. Then all at once, they were outside Mrs Tilney’s door. Ellie took an audible breath and reached for the handle, while Cat, hardly able to breathe at all, turned back to shut the gallery doors behind them.

In that instant, the dreaded figure of the General appeared outlined against the light from the gallery. Before Cat could even groan a warning, the General barked, ‘Eleanor,’ in his best parade-ground voice. It bounced off the stone walls, tiny echoes ringing in Cat’s ears. For a split second she hoped she might have escaped his notice, but knew at once it was a forlorn hope.

‘Fuck,’ Ellie muttered and took off at top speed down the hall. Father and daughter disappeared and Cat took the opportunity to sprint back to her own room, relieved not to see another soul. She didn’t know whether she’d ever dare to leave her room again. But at least she would be clean if she had to leave in disgrace.

Standing in the shower as the water cascaded over her head, Cat resolved that she’d have to get into that room tonight, in case it occurred to the General to lock it up. For all she knew, he’d already done that.

She couldn’t stay in the shower for ever, and when she finally returned to her bedroom, she’d scarcely rubbed a towel over her hair when there was a timid knock at the door. Making sure the towel was firmly wrapped around her, Cat cautiously inched the door open. Ellie stood there, looking on the verge of tears. ‘Can I come in?’ she said.

‘Course you can.’ Cat threw the door wide and welcomed her with a hug. ‘Are we in deep shit?’

‘Not as much as I thought. He’s so distracted with his meeting he hardly told me off at all. He just wanted to make sure I was spruced up and changed—’ She gestured at her little black dress. ‘They’re having cocktails before dinner. You’re required too, I’m sorry.’

Cat looked at her in dismay. ‘I haven’t got anything like that to wear.’

‘I did wonder. It’s not really your style. Look, we’re about the same size. Well, you’re bigger in the bust than me, but we can get round that with the right fabric. I’ll lend you something of mine.’

Half an hour later, Cat was squeezed into a ruby velvet dress. The ruched material hid the fact that it was styled for a different shape and although she felt incredibly self-conscious, none of the four middle-aged men drinking cocktails seemed to pay her much attention. She and Ellie were clearly there for decorative purposes only, and they were able to escape when the men went into dinner. They retreated upstairs to more Sex and the City, but that night it was closer to eleven when they separated, worn out by emotion and exercise in the open air.

As she walked back to her room, Cat heard hearty male voices in the hall below and from her window she saw the headlights of four cars disappear down the drive. In the light of an almost full moon, the park looked eerie but empty. Would the General go straight to bed or would he go to his office? She’d have been willing to bet he wouldn’t be ready for bed yet. He had the habit of working late, she knew, and she imagined he would want to make his notes on the lengthy conversations of the day immediately, while they were fresh in his mind. She cracked open her door and listened hard. For once, there were none of the sounds of the building creaking and settling that she’d grown accustomed to in the short time she’d been at Northanger.

Cat slipped off her shoes and moved cautiously down the hall. At the dog-leg she paused, holding her breath, and peered round the corner. The gallery was empty, and the silence persisted. She seized her courage in both hands and raced to the double doors as fast as she could. She opened them, slipped through and gently closed them behind her. She leaned against them for a moment, heart hammering. Was there any sign of pursuit? The only thing she could hear was the beating of blood in her ears.

She inched forward in the dark, feeling for the door handle. After a few seconds, her hand closed round the knob and she twisted it open. The door swung silently back and in an instant she was inside. Moonlight illuminated the chamber through an array of arched windows that looked vaguely ecclesiastical and reminded Cat of the origins of the building. Although it bled most of the colour out of carpets, curtains and other soft furnishings, it was clear to Cat that this was no punishment cell. It looked like any other bedroom she’d seen in the abbey, except that it contained the small traces of individual habitation that were absent from the guest rooms – a hairbrush on the dressing table, a book and a pair of glasses at the bedside, a bottle of perfume beside them.

There were two other doors in the room. One led to a bathroom that had been stripped of toiletries and medication, the other to a dressing room bereft of clothing. It seemed that all but a few traces of Mrs Tilney had been removed from the room, either to save the General from painful reminders or else to cover his tracks. Then Cat thought of a third possibility. If Mrs Tilney were indeed a prisoner in the tower, she would need clothes and toiletries, no matter what the General’s purpose for her.

Clearly there was nothing to learn here. There was nothing for it but to explore the turret. Luckily she had a spotlight app for her phone which would light her way up the stone spiral that rose inside the turret. Cat crept back to the door and pressed an ear to the wood. She could hear nothing, so she cracked it open and listened again. In the distance, she heard a faint noise that might have been a door closing but it was too far away for her to worry.

Cat edged the door open and slipped through. Darkness again engulfed her as she silently pulled the door to and let the latch slip back into place. She tiptoed down the hall then turned on the bright screen of her phone app. It created an eerie glow, splashing shadows up the walls. But it provided a decent light to climb the stone stairs, so old and worn that each step had a depression in the middle.

Within a few seconds she had rounded the first turn in the spiral. She heard a scrabbling by her feet. Cat stifled a shriek and splashed the light downwards to reveal a tiny grey mouse paralysed with fear. Annoyed with herself, she shone the light upwards again. Ahead of her were more steps but now she could see the way ahead was blocked by a set of iron railings like an old fashioned prison cell, fastened with a heavy galvanised padlock. Cat crept closer, studying the padlock in the phone light. She didn’t know whether to be relieved or disappointed at the cobwebs and dust that festooned the padlock and the nearby bars. It was clear that nobody had disturbed it in a very long time.

Then all at once noise and light seemed to fill the hallway. Swift footsteps clattered up stairs and a bright overhead light bathed her in its brilliance. Even if she’d had time to make her escape, Cat was frozen with fear. The General was coming. The General would not, could not let her get away.

She had never known such paralysing horror. Her legs trembled beneath her and somehow she managed to turn her head. The long shadow of a man was cast into the stairwell ahead of the person himself and she felt her throat close in panic. No weapon, no escape. She was entirely at his mercy.