of the library. Madam Pince, the librarian, was a thin, irritable woman who looked like an underfed vulture.

'Moste Potente Potions?' she repeated suspiciously, trying to take the note from Hermione; but Hermione wouldn't let go.

'And theses fwe books?' Amelia held up her list.

'I was wondering if I could keep it,' she said breathlessly.

'Oh, come on,' said Ron, wrenching it from her grasp and thrusting it at Madam Pince. 'We'll get you another autograph. Lockhart'll sign anything if it stands still long enough.'

Madam Pince held the note up to the light, as though deter- mined to detect a forgery, but it passed the test. She stalked away between the lofty shelves and returned several minutes later carrying a large and mouldy-looking book and seven smaller but just as moldy books. Hermione put it carefully into her bag and they left, trying not to walk too quickly or look too guilty.

Five minutes later, they were barricaded in Moaning Myrtle's out-of-order bathroom once again. Hermione had overridden Ron's objections by pointing out that it was the last place anyone in their right minds would go, so they were guaranteed some privacy. Moaning Myrtle was crying noisily in her cubicle, but they were ignoring her, and she them. Amelia had tried to talk to her, but Myrtle just wailed loudly and dived into a toilet splashing Amelia with water.

Hermione opened Moste Potente Potions carefully, and the four of them bent over the damp-spotted pages. It was clear from a glance why it belonged in the Restricted Section. Some of the potions had effects almost too gruesome to think about, and there were some very unpleasant illustrations, which included a man who seemed to have been turned inside out and a witch sprouting several extra pairs of arms out of her head.

'Here it is,' said Hermione excitedly, as she found the page headed The Polyjuice Potion. It was decorated with drawings of people halfway through transforming into other people. Harry sincerely hoped the artist had imagined the looks of intense pain on their faces.

'This is the most complicated potion I've ever seen,' said Hermione, as they scanned the recipe. 'Lacewing flies, leeches, fluxweed and knotgrass,' she murmured, running her finger down the list of ingredients. 'Well, they're easy enough, they're in the student store-cupboard, we can help ourselves. Oooh, look, powdered horn of a Bicorn – don't know where we're going to get that ... Shredded skin of a Boomslang – that'll be tricky, too – and of course a bit of whoever we want to change into.'

'A bicorn? I have never heard of one of those. It is a unicorn that can talk two different languages or does it just swing both ways?'