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It was late at night and Sirius, James and Peter were sitting in the library finishing off an essay that they had to write for History of Magic. Well, Peter was (Sirius and James had both refused to lend him theirs, but had willingly agreed to accompany him to the library under James' invisibility cloak). James was asleep with his head in a book, his glasses falling off and Sirius was randomly wondering about the library, looking for something to do. Remus was absent; he had "gone to his great aunt's funeral" as he had told his friends before he had left.

'What date is it?' asked Peter who had finally finished his essay and was sucking the end of his quill.

'It's the 31st isn't it?' replied Sirius wandering back to the desk where Peter and James where sitting, 'Listen, I'm worried about Remus.'

'Me too,' said James sitting up straight in his seat, 'I mean, I think he's sick or something. He keeps telling us things that don't really make sense. Like in the past year his great aunt Ruth has died about five times.'

'Yeah,' said Sirius thoughtfully, tilting back in his chair, 'but there's more than that....' a frown appeared on his face, his grey eyes shadowed with thought, 'It's that he looks so much older than he is, and he always has dark circles under his eyes, and he...' Sirius trailed off. It was as if something had just clicked in his head. He stood up suddenly, knocking his chair over in the process.

'Sirius be quiet, you'll wake up Madame Pince and -' started James, but Sirius cut across him.

'Peter, what date did I say it was?' he asked sounding frantic.

'Um, the 31st? Why? Sirius where are you...' but Sirius had already started to move away from them to the other side of the library.

'No.' breathed Sirius.

A ripping sound echoed through the library. A few seconds later Sirius reappeared carrying what looked like some kind of chart.

'Do you know what this is?' he demanded spreading it on the table. James turned it around to face him. He looked at the lunar calendar in front of him and frowned.

'Of course, it's a... you don't... you can't possibly think that... I mean it's Remus!' James looked shocked at the idea.

'Think about it, he disappears every month at full moon – just like tonight. It would explain so much: the disappearances, the age, the violent mood swings-

'- the tiredness -'

'- the mysterious scar on his face -'

'- the fact that Kavanagh hates him so much!'

'Yeah,' said Sirius, 'that's probably why he makes us do all of those essays on how to recognise a werewolf!'

Peter gasped. Clearly he had not seen where the conversation was going.

'Sirius, don't be so mean! Of course Remus isn't a w-werewolf! R-right James?, Peter looked at James uncertainly.

'I think he might be, Pete,' said James trying to sound reassuring, 'I don't see how we didn't figure this out before now. I mean look at all the signs! And all those essays we did, what did we find out?'

'Werewolves in human form have large canine teeth, thick fingernails, auburn hair and amber or hazel eyes and in some cases scars inflicted by themselves. All true for Remus,' Sirius told them, but then a shadow appeared on his face again, 'There's just one thing though. Why didn't he tell us?'

At Sirius' words, they fell into a thoughtful silence.

Then Peter spoke, 'I still don't believe you, he just couldn't be a... a werewolf.'

Sirius looked at him and sighed. He didn't believe it because he didn't want to believe it. Peter was scared.

'Well, there is only one way to find out for certain,' said James grimly, 'we're going to have to confront him.'