He didn't even like the cat who claimed to be Cleopatra, she wasn't his type at all! Besides, he was a wizard, and wizards didn't have 'a type' so much as one person they fell in love with for a lifetime, usually as teenagers. If the love of your life didn't feel that way about you, or you split up with them, or they died, then not having a partner or children of your own meant you became a teacher at Hogwarts.

Or did he just assume this was the norm because he and most of his colleagues at Hogwarts were in this situation? Still, he hadn't known many magical adults in his universe who had had multiple partners, apart from Blaise Zabini's mother the serial killer. He had never bothered to ask Albus Dumbledore's portrait whether the rumours were true that he and Gellert Grindelwald had been more than just good friends when they were teenagers back in the 1890s, but nobody could recall Dumbledore having a boyfriend any time within the 20th century.

If, sometime in the 1920s or so, Dumbledore could have fallen in love again, the way Muggles did, and this time had found a good husband, someone who could argue with him as an equal and be a moral compass to him, what sort of man might he have been by the time he was 90, when Severus started at Hogwarts, or 100, when Severus returned there as a teacher? Had he ever even been capable of loving anyone anyway? Or had he just been born a psychopath, incapable of caring about anyone, a man who couldn't possibly be sincere in regretting that he had caused his sister's death, because psychopaths don't have regrets? Or was Severus just projecting a stereotype of 'this is what psychopaths are like' onto a man who was more complex than that label, the same way that most people would assume that Konstantine or Anakin couldn't possibly feel regret or remorse or love?

He didn't know. He didn't need to know, he reminded himself. Neither Albus Dumbledore nor anyone else in his own world had any call on him. Except that Lily did, because he still loved her, and she had rejected him, and that meant he couldn't possibly fall in love with or be friends with or trust anyone else ever again, and so he had to push away anyone who tried to befriend him. Cheiron, obviously, because he was in charge, and authority figures weren't to be trusted. And Anakin Skywalker, because he had dared read Severus's memories – not just that night when they were watching the Pensieve, but when Severus had gone away into that other place deep in his own mind to find a place to die of loneliness because nobody cared about him or would ever seek him out.

Then there had been Nutt, before Anakin. He'd been all right when he was just a lab partner, but when it came to Nutt talking about his own experience of being treated like a monster just because he was an orc, and feeling that he was worthless and had to build worth by being useful, and how he had learned to accept himself, there had been just too much danger that Severus might start liking and trusting him, and then he would be heartbroken when Nutt inevitably rejected or betrayed him the way everyone always had. Severus had had to push him away. And Nutt had accepted it, which just went to show that he did hate and despise Severus, and that Severus's ending the friendship first had been the right thing to do.

Why were all the people he met here male? He'd talked to a few witches from other worlds, but – well, he respected Esme Weatherwax a lot, but he felt too much in awe of her to confide in her. Weatherwax didn't mope around over lost love. There had been a wizard boy, Mustrum Ridcully, who had been sweet on her when they were teenagers, but she had been too busy learning to be a witch to have time for boys, and he was busy with his own magical training, and Ridcully had gone on to become the Head of the premier magical school on the Disc, a job which had had an even shorter life expectancy than being Defence Against Dark Arts master at Hogwarts until he took over, and Weatherwax had grown to be a powerful and good witch who had defended the kingdom against every conceivable supernatural hazard when necessary and in between times had got on with being a responsible, hardworking Healer to her Muggle neighbours, and she insisted that she had absolutely no regrets about how her life had turned out, and who would dare argue? She wouldn't appreciate some wizard crying on her shoulder.

As for Weatherwax's younger colleagues, like Ages Nitt and Magrat Garlick – well, Magrat had a head nearly as full of airy-fairy notions as Luna Lovegood or even Sybill Trelawney, but she was one of the few Discworld witches Severus knew who actually bothered to learn much about Herbology and proper potion-brewing technique, and she liked books, and – if he'd got to know her better, they might have become good friends, and perhaps he might have found that he could fall in love again, which would be a very bad idea considering that Magrat was happily married to a Muggle she dearly loved, and they had a child called Esmerelda Margaret Note Spelling, which had been an accident (the name, not the daughter) but which Severus thought wasn't a bad name for a girl who might well have inherited magical talent. And – when Severus and Magrat had once talked about more than trivial things and he had asked her why any witch would choose to marry a Muggle, and didn't she realise that all Muggle men hated witches and that Verence was bound to hate and mistreat her and Spelly sooner or later, they had had an argument about it. When Magrat had come to apologise and try to make up and be friends again, he had avoided seeing her. When a witch got angry with you, the friendship was over, and he wasn't going to make the mistake of thinking reconciliation was possible.

Severus couldn't breathe. He wondered why not, until he realised that his face was pressing into the pillow. He pushed himself up on one hand… He hadn't even realised that he had shifted back into human shape. Was this what came of thinking human thoughts? He couldn't allow his mind to stay too feline at night, but if he let his body revert to being human, they would just be back to the status quo. He kneaded the pillow with his paws until he felt properly feline again.

He wasn't ready to go back to sleep. He sprang down from the bed, squeezed through the gap in the slightly ajar bedroom door, and padded down the stairs, through the cat-flap, and out into the night.

Before he had gone far, he met a tabby cat he hadn't seen before. She had a white face and white paws with black underpads, and looked as if she might have Siamese or Abyssinian ancestry. 'Hello,' she said. 'Are you new around here? Mehitabel told me about you. I'm Jennie, by the way – Jennie Baldrin.'

'Severus Snape. Is Mehitabel the one who claims to be a reincarnation of Cleopatra?'

'That's right. Take no notice, she's all posture. But – you're one of those cats who genuinely used to be human, aren't you?'

Severus's fur bristled. 'I have no idea what you are talking about.'

'Oh, come on! You're not difficult to spot, if we've met one of you before! I used to have a friend who had been an eight-year-old boy and turned into a cat when he was nearly killed in a car accident, and of course his family just assumed he was a stray and threw him out. Well, at first I thought he was just an ordinary house pet whose humans had got tired of him and abandoned him, and as I'd been a stray for a few years and he was new to it, I thought I'd adopt him. But it wasn't just that he didn't know how to survive as a stray – he didn't know anything about how to be a cat, not how to groom himself or even how to lap milk. He was as helpless as a newborn kitten. So I took him under my paw and we were together for a while – we even got jobs together as rat-catchers on a boat, and travelled from London to Scotland and back. But then – when a tom I didn't like was bothering me, and Peter – my friend – fought him for me, he nearly died, and he turned back into a human, and he just forgot I existed. Maybe he thought I was just a dream he'd had while he was ill.

'I saw him a bit later on, when he was getting better, sitting in a chair outside the block of flats he lived in, with a black and white kitten in his lap. I'd never seen him as a human, didn't know what he'd smell like as a human, but I knew it was him, and so I said hello, and all he said was, "Hello, puss." He clearly didn't have a clue who I was, and Smudgie, his new cat, just told me to find my own human because Peter was hers. It was as bad as – no, it was worse than when I lost my original human. I used to live with a girl called Buff, but she lost me, and I thought she'd abandoned me. When we found each other, years later, I was with Peter by then, and Buff would have loved to have me back, but her parents wouldn't adopt Peter as well, and I chose Peter over her. And then it wasn't more than a few months before I lost Peter as well. That's what happens, if you let yourself love a human.'

'Yes,' said Severus, with feeling.

'You've been abandoned, too, haven't you?'

'Yes. There was a human girl who liked to play with me, as long as she didn't have anyone else to play with. But when she started making new friends, she had less and less time for me as the years went by, but when I made new friends of my own, she didn't like them. And one day, we quarrelled, and we both called each other horrible names, and when I tried to apologise later, she wouldn't listen. She said she'd been making excuses for me for years and none of her friends could understand why she even talked to me and it was too late now.' In some ways, he felt glad now that Cheiron had given him his memories back. Horrible as they were, at least they were a reminder that not everything had been his fault.

'That's humans,' agreed Jennie. 'Not Buff, I mean, but some of the children my friends have known – they'll pull your tail, dress you up in dolls' clothes and try to teach you to swim in the bath-tub, but if you scratch the little darlings once, you're out on the street if you're lucky, or thrown in the river in a sack with a brick if you're not. Are you ever going to turn back into a human?'

Severus would have liked to say, 'Of course not!' He would have loved to get to know Jennie better, and it was obvious that she had been heartbroken too many times by humans to risk letting it happen a third time. But he had needed to lie and cheat all his life as a spy, and he was sick of it. The Rock was a place to be honest. He had turned back into a human once that night without even meaning to, so how could he promise that it wouldn't happen again?

'I have not yet decided,' he said. 'But…'

'Well, I'd better be off, then,' Jennie said briskly, trying to sound as though she wasn't disappointed. 'I'll be all right – if I get lonely, there are plenty of real animals around to talk to.'

'Wait – I won't forget you…'

'Severus!' came a familiar, deep-voiced bellow. 'Severus! Are you all right?'

Severus sighed. 'Can't I even go out for a walk without you panicking that I've fallen off a cliff?' he miaowed. Turning back to Jennie, he tried to explain. 'This is Konstantine – one of the humans I live with now. He's brought some milk for my breakfast. Do you want to share?'

But Jennie had gone.