About fifteen minutes later, they walked back to the Slytherin common room together, holding hands all the way. Neither spoke: they were both stunned into blissful silence. Marisa had never felt anything like it: all she needed in the world was the feeling of his hand in hers.

"Wipe that goofy grin off your face," said Marisa finally when they had just reached the corridor. "People will get suspicious."

Leo took a deep breath to compose himself and then said to the portrait "Silver leaves". It swung open and they stepped inside.

"What's going on here?" asked Marisa, staring around, wide-eyed: practically every student was there, all with their wands out and aimed directly at her chest.

Draco sat in the centre of the packed room in one of the two best armchairs, the other empty beside him, an unbearably smug grin on his face. "We're ridding Slytherin House of its Mudblood scum. Namely, you."

She fought hard not to look at Leo, to ask what his plan was and if it had any realistic chance of success, and succeeded. "Are you?" she asked.

"Leo," snapped Draco. "Over here."

Leo walked wordlessly over to Draco and sat down in the other armchair.

"Wand out," said Draco.

Leo pulled his wand from his pocket and pointed it at Marisa.

"Is everyone against me?" asked Marisa.

No-one moved for a second, and then Draco said "Yes. The whole of Slytherin is against Mudblood scum."

"Theo?" she asked.

"You're a Mudblood. We need to get rid of you." His response was almost mechanical, like he said it without thinking, just repeating the slogans he'd been fed.

"Tracey?"

Tracey wordlessly shook her head.

"Daphne?"

"I – I can't."

She'd purposely left Leo until last. She knew he wouldn't refuse to help her. "Lord Asriel," she said finally. "Surely you, at least, have the sense to realise that this shouldn't be happening."

Leo looked up and met her eyes. He was the first person to have done so in the entire room. "Marisa," he said, "surely you must understand that it would be impossible for the Lord of one of the most ancient families of the country, with a proud pure-blood tradition, going back centuries, to support a Mudblood over his entire House? And that I could never be seen to do so?"

Marisa felt as if a weight had settled on her stomach. "Of course, Lord Asriel," she said, bowing her head. "It was foolish of me to have asked." She reached into her pocket for her wand. If she was going to be defeated she'd at least deal some damage of her own first.

Then Leo stood up and walked towards her. "I will help you, Marisa. Anyone who so much as touches a hair on your head will have me to answer to."

A thousand contradictory thoughts flashed through Marisa's head: what was he doing? He'd just contradicted himself – what was his plan? How was he going to get out of this?

"What the hell d'you think you're playing at, Asriel?" snapped Draco.

"Isn't it obvious?" asked Leo. "It's basic logic, you're meant to be Slytherins! Work it out! I won't help a Mudblood. I am helping Marisa. Therefore…"

And then she realised. It was a brilliant plan, and she couldn't believe she hadn't thought of it herself at least a year ago. "You said you wouldn't tell anyone!" said Marisa, turning to Leo in fake anger.

"Don't be ridiculous, it's gone much too far. You always said you were going to reveal it at some point, anyway, and you might want yourself to be jinxed to pieces, but I don't."

Draco still looked confused. "Therefore, you're being confusing to mess with me and try and trick me out of making her suffer."

"Wrong. Although not unreasonable. Marisa's the one who's been messing with you, ever since you first met her. Telling lies without actually lying."

"Oh, very well," said Marisa, rolling her eyes. "I am not a Mudblood."