The High Street was still busy. Round the last corner, into Talbot Street. I was tired now, I would need to concentrate extra hard on the checking so I didn’t make any mistakes.

Into the alleyway, round to the back of the house. I looked up at the windows, all of them, the balcony with the eight panes of glass showing, the bedroom, curtains shut tight. Stuart’s flat had one light on in the bedroom. I’d put one of my timers up there. It would go off at eleven. Downstairs, Mrs Mackenzie’s flat was in darkness. It all looked okay. I carried on to the end of the alleyway, round to the front of the house.

When I’d got in, shut the front door, it occurred to me that I was the only person in the house. I’d be the only person sleeping in the whole of this great big house tonight. No Mrs Mackenzie, no Stuart. Just me. Last night I’d ended up talking to Stuart for what amounted to hours, so it felt as if he was here; it didn’t feel as if I was alone. Tonight felt different.

I checked the door, running my fingers along the edge, feeling for anything, any bumps or swells, which might indicate the door had been tampered with. Then the latch. Then the lock. Turn the handle, six times one way, six times the other way. I missed the sound of Mrs Mackenzie’s television. I missed her coming out to see me.

I paused at the end of the first set of checks. This was normally the point at which she would open her door behind me.

I’m not sure if I felt something, or sensed it: a draught, maybe, a scent of food cooked a long time ago, a breath of cold air. I turned slowly and looked at the door. We’d shut it, and locked it, the night that Mrs Mackenzie had been taken off in the ambulance. Stuart had phoned the management company that looked after the lease, told them what had happened. They were going to send someone over to collect the key, but so far nobody had turned up.

I frowned, squinted. The door looked odd.

I went a bit closer.

It was slightly open, a tiny sliver of blackness showing beyond the doorframe. I felt the draught again, definite this time, a whisper of cold air coming from inside.

I pulled at the door handle and it swung open. It wasn’t locked. Inside, everything was dark, dark as the grave.

I shut the door again, firmly. The latch caught and when I turned the handle this time it didn’t open. Stuart’s spare set of keys were in my bag. He’d put the key to Mrs Mackenzie’s flat on the ring along with his other ones.

I found the keys, slotted the right one in the lock and turned it. I rattled the handle. I turned the key in the Yale lock and the mortise lock held the door fast. Right, it was definitely shut and locked. If anyone was inside they would need a key to get out.

I went back to the front door for my second set of checks. It didn’t do the trick, though, because all I could think about was the door to Mrs Mackenzie’s flat, which I’d turned my back on. What if I hadn’t locked it properly? What if the door had swung open again while my back was turned? What if it opened again by itself when I wasn’t looking?

I checked it again. It was still locked. I tried the Yale lock.

I checked the front door for a third time, to balance it all out again. Finally I felt better. I went up the stairs and let myself into my flat. The dining room light was on, as I’d left it, the rest of the flat dark and chilly. I waited for a moment just inside the door, listening to the sounds of the house, straining to hear anything unusual, out of place. Nothing.

I started checking the flat door, feeling vaguely uneasy but not sure why. I couldn’t get over the thought that I was on my own. Completely on my own.

By the time I finished the checks it was nearly nine. I’d been expecting to find something wrong, but everything was exactly as it should have been. It was just as well.

Finally I sat down to phone Stuart.

‘Hey, it’s me.’

‘At last, I was about to give up hope!’ He sounded tired.

‘How’s your Dad doing?’

Stuart sighed and dropped his voice a little. I could hear a television faintly in the background. ‘He’s alright, really. He’s a lot frailer than the last time I saw him. I don’t think Rach really notices it, she sees him every day.’

‘Did you get to the garden centre?’

‘Yeah, but it’s raining. Ended up looking round the greenhouses mostly. You wouldn’t believe how many different plants that man can look at and not get bored. And it’s bloody cold up here, too. I really miss you, Cathy.’

‘Do you?’ I felt my cheeks flush, realising at the same time that I was missing him, too. Even if we hardly saw each other during the week, with him being away I felt the absence of him like an ache.

‘Yes. I wish you were here.’

‘You’ll be back Sunday night. It’ll go fast.’

‘It won’t. Not for me, anyway. What are you going to do with your Saturday?’

‘I don’t know. Go to the launderette. Go for a run, maybe. I haven’t been for a while.’

There was a pause. ‘So it went well? Your session with Alistair?’

‘It was fine. I’ve got homework to do – scoring everything. You know.’

‘And you’re feeling alright now?’

I knew what he was getting at. He was trying to gauge the likelihood of my discussing my symptoms leading to a panic attack later on. ‘I feel fine about all that. I’m feeling more nervous about being here on my own. I mean, no Mrs Mackenzie downstairs, no you upstairs. Just me and the ghosts.’

‘Peaceful, you mean.’

‘Yes. Oh, but there is one thing. We did lock her door, didn’t we? I mean, we locked it with the key?’

‘We did. Why?’

‘The door was open when I got home. Mrs Mackenzie’s door, I mean. It was actually slightly open.’

‘The management company must have been in, then. They said they were going to, didn’t they?’

‘Yes, but surely they were supposed to lock it up, not leave it open.’

‘Maybe they just weren’t as careful. Anyway, I’m betting it’s well locked up now!’

‘I hope so.’

‘Cathy, you locked it. It’s fine.’

I didn’t answer.

‘When I first met you, you did all this alone. You locked yourself in every night, checked the doors were secure, and you were fine. You’re fine now, it’s no different.’

I tried to sound cheerful. ‘Yes, I know. I’m alright, really I am.’

‘Will you come with me to Aberdeen next time?’

‘Maybe. If you give me a bit more notice.’

‘Rachel’s dying to meet you.’

‘Stuart, honestly. Did you tell her about the OCD?’

‘No. Why, should I?’

‘I just want to make sure she has a full and accurate picture.’

‘The OCD isn’t part of you, is it? It’s just a symptom. Like snot is part of a cold.’

‘Lovely. What have you been telling them, then?’

‘I’ve told them I’ve met this girl with silver hair and dark eyes, who is funny and clever and charming and occasionally spectacularly stroppy. She can put away fifty cups of tea a day and outstare someone with glass eyeballs.’

‘Now I see why they’re dying to meet me.’ I tried to fight back the yawn but it was impossible.

‘Am I keeping you up?’

‘I’m really tired. Sorry. I didn’t sleep last night, and I walked back from that place today, the buses were all jammed in traffic.’

‘You walked back from Leonie Hobbs House?’

‘Give over, it’s not that far. I like walking.’

I yawned again.

‘Take the phone with you when you go to bed, okay?’ he said.

‘Why?’

‘If you wake up in the night, ring me. Will you?’

‘I don’t want to wake you up, that’s not fair.’

‘I don’t mind. If you’re awake, I want to be awake with you.’

‘Stuart. This is all really weird.’

‘What do you mean, weird?’

‘When you come back on Sunday, it’s not going to be the same, is it? It’s all changed. Since the other day.’

‘Since I kissed you, you mean.’

‘Yes.’

‘It has changed, you’re right. I was bloody determined to keep my distance so you could concentrate on getting better. I don’t think I can do that any more. Does that worry you?’

‘I’m not sure. I don’t think so.’

‘My flight gets in at nine-something on Sunday night. Can I come and see you when I get back home? It’ll be late.’

It was that moment, that turning point.

I hesitated before answering, knowing what it would mean if I said yes, and what it might mean if I said no.

‘Cathy?’

‘Yes. Come and see me. I don’t care how late it is.’