A few minutes later, everyone had arrived and Marisa was one move away from victory. "Rook to g8," she said with a grin. "Checkmate."

"Impressive," said Granger.

"Well done," Potter agreed, looking only a little grudging.

Leo and Weasley, on the other hand, were still going. Neither side looked likely to force checkmate within the next few moves, or, possibly, at all.

Leo sighed, knowing what he had to do but reluctant to concede not having won. "Would you like a draw?" he asked, managing to sound not completely grudging.

"Sure," said Weasley, shaking hands. "Good game. You were better than I expected."

"Likewise," replied Leo, quickly packing the pieces away and standing up. "So, everyone, you probably already know our guests, but if you don't, they are Harry Potter, Ron Weasley and Hermione Granger. They want to join our group. Obviously, this goes against our rule of Ravenclaws and Slytherins only, but I wondered if we could make an exception. So we're going to have a democratic vote. All those in favour of allowing them to join, raise your hands."

A flurry of hands went up: nearly all of the Ravenclaws and a couple of first-year Slytherins, plus Marisa and a tentative Daphne.

"All those against?"

Quite a few hands went up, including Theo's and Tracey's, but they were most definitely in a minority.

"Then I declare the motion passed," said Leo.

Theo swore very loudly. "We can't let them into our group," he spat. "I mean, Mu – ggle-borns are bad enough, but Harry bloody Potter, are you serious?"

Leo sighed. "We had a vote, that's democracy, and I am bound to carry out the results of that vote. If you don't like it, you can leave."

"You know what? Sure. I'm about done with you crazy people, you're not worthy of the name of Slytherin." And with that, he marched back up to the castle. He was followed by his cousin Matthew.

"Good riddance," said Morag, smiling.

"Sorry," said Leo, feeling a little awkward. "Not all Slytherins are like that."

"No, some are worse," added Marisa. "The ones left here are mostly all right, though. Crazy, sure, but not die-hard blood purists. Anyway, can we get on with the lesson now?"

Leo nodded. "It's been a while since our last meeting," he said, "so I thought we'd just revise what we worked on before Easter instead of trying anything new. But first I want to get an idea of the skills of our new members… fancy a duel, Potter – err… Harry?"

Harry nodded, somewhat nervously.

"And then… Marisa and Ron, and… Daphne, d'you want to go with Hermione?"

"Sure."

The three pairs faced off against each other, and all six of them bowed low before the duels began.

Harry's opening move was a simple Disarming Charm, which Leo dodged easily before returning the attack with a Full Body-Bind, also dodged. Then Harry began to fire faster, making it trickier to dodge.

"Protego," cast Leo quickly, and the Disarming Charm bounced off Leo's strong shield. Harry was only just able to get over his surprise in time to dart out of the way, and then he began firing hexes and jinxes at the shield as quickly as he could.

Leo knew this wouldn't work, though: he'd tested it against Marisa and Harry's magic might have been stronger, but it was less well-controlled and he was using a lot of energy – and distracting himself.

In one rapid motion, Leo jumped to one side so he could fire out from behind the shield and cast a rapid Full Body-Bind. He was right about the distraction and the spell's pale white light was harder to see if you weren't looking for it, so it hit Harry right in the chest.

He allowed himself a brief moment's triumph before releasing Harry and checking to see how the other two duels were going.

"No – " gasped Ron, in between desperate giggles. "Please – stop!"

Marisa had evidently hit him with a Tickling Charm, and judging by the look on her face was very much enjoying it.

"You should probably stop, Marisa," said Leo.

"Fine," said Marisa, lifting the Charm with more than a hint of reluctance.

Ron scrambled to his feet, looking exhausted and shocked. "Blimey," he said. "That was…"

"Brilliant?" suggested Marisa half-jokingly.

"I was thinking more of evil," he corrected.

"Yeah, she's evil," said Leo, turning to watch Hermione and Daphne, the only pair who were still going: Daphne's Shield Charm had failed to hold up and now the two girls were much more evenly matched.

"I give up," said Daphne, gulping for air. "Draw?"

"Draw. I had no idea how – how much you'd been doing, how far ahead you were, it feels kind of unfair we haven't been learning any of this stuff in class."

Leo rolled his eyes: typical Hermione Granger. "It's fine," he said. "I don't think we're going to need any of these spells – for classes at least – for at least another year or two. But you'll catch up quickly. So, where d'you want to start?"

"Shield Charm," said Harry instantly.

"Okay," said Leo. "Marisa, d'you want to help me teach them? Terry, Daphne, if you could take the others through some exercises, have another look at Fumos and keep working on Disarming for the first-years."

Marisa nodded, looking perhaps a little too keen on the idea.