Severus smelled Jennie's scent in various places around the island when he went out for walks. He forced himself to resist the temptation to track her like a bloodhound. If he had been capable of not stalking a girl who had rejected him when he was a hormonal sixteen-year-old boy, he was certainly capable of self-control when he was – uh – a hormonal sixteen-week-old kitten. After all, Jennie would smell his scent, too, and was quite capable of approaching him if she wanted to talk to him, but she evidently didn't.

One night when, yet again, he had set out for a walk because he was too restless and miserable to sleep alone and wouldn't allow himself to cuddle up against his housemates for company, he was too busy focusing on not tracking Jennie, and also not hunting any of the rodents he could smell, that he barely noticed that it was a bright, moonlit night. Then another scent, hitting his nostrils like a Stinging Hex, brought it to his attention.

Werewolf! More to the point, a werewolf in wolf form. There weren't any trees nearby, but he managed to leap to the edge of the roof of a low-lying building, run up to the ridge and perch on it, back arched and fur on end, hissing angrily, before he even had time to be angry with himself for being so careless. How could he have forgotten full moon?

'Oh, relax!' came a voice from ground level. 'I don't chase cats! Chickens, now, that's a different matter. Florence can't resist barking at cats, but she'd never harm you. I'm afraid most werewolves are a bit dog-like – it's inevitable, when you're a wolf who lives with humans.'

Severus recognised the voice, even before he dared glance down at the wolf with the long golden fur. Angua von Überwald. Officer of the Ankh-Morpork City Watch, girlfriend of Captain Carrot Ironfoundersson, and often to be found on the Rock hanging out with her friends Florence Ambrose and Sergeant Taura, and sometimes a few others like Lonesome, the put-upon werewolf companion of the wizard-boy Xar, and Wolfboy of Bordertown.

Severus had once dreamed about painting portraits of the three wolf-women into a mural on his bedroom wall, but he had only ever risked watching them from a distance, and up until now he had been careful to stay inside at full moon. Why wasn't Angua kept securely locked up? Admittedly, she probably wasn't that much of a threat to Severus personally right now. Considering that Remus Lupin had spent his teens running around with three chums in the forms of a dog, a stag and a rat, werewolves seemed to prey on only one species. 'How are you with humans?' he asked.

'Do you think I'd be allowed to work as a police dog who can be her own handler if I couldn't behave responsibly around humans?' retorted Angua. 'Or that I'd have a human boyfriend who feels completely comfortable letting me sleep in a basket next to his bed, if there as any likelihood that I might jump up and rip his throat out? We don't all turn into ravening berserkers at full moon, you know. In my world, if some werewolves are monsters, it's because they choose to be evil, just as bad humans do. And that makes them all the more dangerous, as you can imagine.'

Severus was too flooded with fear-hormones to imagine anything more terrifying than Remus Lupin unmedicated at full moon. He groped for human, rational thoughts in his brain – but, both as a cat facing a large dog, and as a human who had nearly been eaten by a werewolf as a teenager, he couldn't find anything approaching dispassionate logical thought.

'If a berserker werewolf is locked in a secure basement, they might scream and bang their head on things and bite themself, but they're not likely to get out,' Angua continued reasonably. 'A real wolf would pace around for a bit, establish that there's no way out, and go to sleep. An intelligent werewolf will find a way to undo the lock.'

Her voice was calm, but her hackles were rising. Severus guessed that Angua, too, had had bad experiences of werewolves. Had she been bitten as a child and infected with lycanthropy, like Lupin? Or was her condition genetic? He had gathered from overhearing their conversations that Wolfboy was the victim of a botched curse which had been meant to Transfigure him into a dog, and that Florence and Taura were genetically engineered experiments; Florence's genetic parents were normal wolves and her birth mother was a St Bernard dog, while Taura had, like so many people in Konstantine's universe, including Konstantine's daughter, been gestated in a uterine replicator. And he had heard them talking to an Australian boy who had a genetic form of lycanthropy where only the seventh son of a seventh son in certain families with Portuguese ancestry was a werewolf.

But yes, come to think of it, he had heard Angua mention coming from a long family of werewolves, most of who held anti-human prejudices. He got the impression that werewolves where Angua came from hunted humans for sport, not the way that a pure-blood supremacist might hate Muggleborn wizards and persecute them as enemies, but more the way that many wizards would torment Muggles, because they saw Muggles as not really people at all.

'Do berserkers come here?' he asked. The rules of the Rock meant that he was unlikely to meet Remus Lupin or Fenrir Greyback or any other werewolf he had known personally in his lifetime, but there were plenty more of them.

'They don't come here as berserkers,' Angua said. 'This is where their minds go to when their bodies are out of control. They generally only appear here as humans, if they don't have any experience of being in wolf-form with a sane mind. It's tough on them – they have the worst consequences of being a werewolf without most of the enjoyment. But Toby says compared to the vampires and zombies in his world, werewolves are the lucky ones, because at least they're healthy when it isn't full moon, instead of being dead during daylight hours and really ill the rest of the time.'

'Is Toby the Australian one?'

'That's right. Nice kid.'

'I'll take your word for it.'

'Anyway,' said Angua, hastily changing the subject, 'Have you seen Jennie lately?'

'She ended our friendship.'

'She misses you. Anyone with half a nose can smell that.'

'Has she told you she misses me?'

'Not in those words. But she asked me whether I'd seen you, and how you were.'

'So she sent a tracker dog to keep a nose on me. How charming.'

'You miss her, don't you?'

'That is irrelevant. She could love me if I were a cat who had once been a human, but not as a human who sometimes takes the form of a cat. I am caught between two worlds.' As he had always been: a wizard child in a Muggle town; a half-blood in Slytherin whose best friend was a Gryffindor; a half-blood Death Eater; and a spy passing between the Death Eaters and the Order of the Phoenix and convincing each side that the other firmly believed that he was a double agent who only pretended to be on this side, and knowing that whatever he did for one side would cause suffering to people he cared about on the other side. But, yes, Jennie might love Severus the cat if he could wholly abandon being human wizard Professor Snape, just as, in the memories they had been watching, Elli could love Admiral Naismith but would never agree to marry Lord Vorkosigan.

'Do you think I don't know how that feels?' demanded Angua. 'My first boyfriend was a wolf, and my current boyfriend is a human by birth and a dwarf by culture. My best friend in the Watch apart from my boyfriend is a dwarf. Humans and wolves don't like werewolves, and dwarves really hate werewolves. Sometimes I think I can't go on any longer with a relationship with a lovely man who knows what I am, knows what my family are like, loves and accepts me for who I am, and deserves better than a werewolf who might go rogue and need to be put down, like my brother Wolfgang. But yet, no matter how many times I keep telling myself that someday I'll have to break up with him, that day is never today.'

'Jennie has broken up with me. I cannot get back together with her if she does not wish it.'

'No. And maybe that's part of what she likes about you. Most toms wouldn't think about what she wanted. A good human can.'

'We are not the same species!'

'Not always. Not all werewolves can shapeshift fully,' Angua continued. 'My sister Elsa and my brother Andrei were born unable to shift at all.' Her hackles rose again at the thought of her siblings, but her ears were lowered and her tail curled along her hip, as if she was both angry and sad. Severus wondered whether another member of Angua's family – probably Wolfgang – had murdered them, the way some pure-blood wizarding families murdered Squib children, the way Miles Vorkosigan's grandfather would have murdered him given the chance. 'But some shift part of the way. There's a couple I know, where the husband looks like a normal wolf most of the month but turns into a man-wolf-hybrid creature at full moon – looking like Wolfboy or Lonesome, though at least he can speak human language then. And his wife looks like a normal human most of the month, but turns into the same shape of woman-wolf-hybrid at full moon. So they're lovers at full moon, and dog and owner the rest of the time – like the reverse of the relationship Carrot and I have.

'If Jennie comes to the conclusion that she can trust you not to abandon her, she might be able to live with having a boyfriend who is only sometimes a cat. She tells herself she hates humans, but it isn't as simple as that. She loves humans more than almost any cat I know, which is why being rejected by a human hurts her so much. If you're not like that, you need to prove it to her.'

Prove your loyalty. Prove to the Malfoys that you're on their side by helping Draco murder Dumbledore. Prove to Dumbledore that you're on his side by euthanasing him when he requests it. Prove to Harry Potter that he should trust and listen to you, when he's just seen you apparently murder Dumbledore. No. He didn't have to play this game any longer. If Jennie wasn't going to trust him, he'd just accept that he would always be alone.

He ran to the other end of the rooftop, from where it wasn't too big a leap to another, higher roof. By the time he ran out of buildings and had to return to ground level to make his way home, the werewolf was well out of scent range.

Nobody had ever done anything to show that they cared about him as a person and not just a useful tool, he reflected, as he smelled the remains of a saucer of milk that Konstantine had left out for a cat who fulfilled no useful purpose in a world where rodents talked and didn't breed uncontrollably and need culling. Maybe they liked him as a cute kitten, but nobody would have time for him if he went back to being human, he reminded himself as he passed through the proto-garden of compost that Konstantine (who had never shown any sign before of having a soft spot for cute kittens) had carted over, barrowload by barrowload, for the sake of a cat who could have no use for it now except as an outdoor litter-tray, because Severus had told Anakin that if he ever went back to being human he'd like to create a flower-garden just for the beauty of it. It wasn't as if Konstantine ever spared a passing thought for Severus now that he had Anakin to worry about, he fumed as he passed his housemates' bedroom, and heard Konstantine, still awake, call, 'All right?' and Anakin's raspy voice reassure him, 'He is angry but unharmed.'

His housemates' bedroom door stood ajar, just wide enough for a small cat to slip inside and curl up against either of the sleeping men. Severus went to his own room and jumped onto the bed. He longed for Jennie's touch – not for sex, not now, but for her to groom his fur like a mother, and to let him groom her. It would be more intimate than sex between cats was ever likely to be. He groomed himself, pretending it was Jennie's tabby-and-white face licking him, until he calmed down enough to fall asleep.