"And that," said Marisa with a smug grin, "is why you always watch your back. Nice work with that duel, by the way, but don't think you're ever getting within a million miles of me."

"Let him go," said Harry.

"But if I do that, he'll attack me," replied Marisa with an innocent, disarming smile. "Now, let's see how well your shields hold up to a real attack, not Leo's pathetic attempts."

All three Gryffindors looked very nervous, and with good reason. Harry, however, nodded and cast a Shield Charm.

Marisa attacked mercilessly, forcing as much power as she could into the spells and firing them off as quickly as she could. She felt her mind slip into the instinctive, almost unconscious frame it needed for duelling, knowing without thinking how to twist her wand and which spells to use and where to dodge.

The shield went down after only three spells and Marisa's next Full Body-Bind made contact. She grinned. "Who's next?"

Ron and Hermione glanced at each other before Hermione whispered something in Ron's ear and he said "I'll go."

They might be learning fast, but they were still very much Gryffindors and had no subtlety whatsoever. They were definitely plotting something. Pretending not to realise, she fired a Disarming Charm into Ron's shield, followed by a Full Body-Bind. As she fired the third spell, a Jelly-Legs Jinx, she heard a whisper of "Expelliarmus!" from behind her and lunged instinctively to one side, her spell missing the shield and fizzling out.

Hermione had reversed the Full Body-Bind on Leo, and true to her prediction he was attacking her. It would soon be four against one. She needed a plan.

She aimed two swift Full Body-Binds at Ron, the first shattering the shield and the second hitting him in the chest, and without pausing sprinted over to the main group. "Daphne! Help me!" she said desperately. "They're all teaming up on me!"

"I'm on it," said Daphne, aiming a Disarming Charm at Leo, who was chasing after her.

"Me too," added Morag, throwing up a shield to protect the three of them.

Tracey, on the other hand, immediately attacked Marisa with a Full Body-Bind.

Marisa dodged quickly and Daphne took Tracey down with the same spell.

"We need a proper strategy," said Marisa. "Who's with me?"

Anthony, Ollie and Roger raised their hands, as did about half of the first-years.

"Okay. Pair up, one shield, one attack," she said. A simple strategy, and perhaps not the most effective, but the best she could come up with on the fly. "And Leo is mine," she added.

The situation quickly dissolved into chaos: everyone recognised the cue for a battle, and Leo's supporters immediately attacked Marisa's.

Leo himself was bombarded by spells as he hurried towards the main group – the downside of Shield Charms was that they were useless when you were moving. He dodged most of them but was hit by a stray Jelly-Legs Jinx from Anthony which sent him to the ground. By the time he'd managed to cast the counter-curse and get to his feet, Marisa had arrived.

One near miss with a Full Body-Bind later, he abandoned his attempt to move forward and threw up a shield. Then he took a calculated risk and cast "Fumos!", conjuring a smoke screen so Marisa couldn't see to aim her spells.

He cast through his own smoke screen and around the shield, taking guesses to Marisa's location and hoping she wouldn't be able to see the spells coming.

"Really, Leo, that is not a very effective strategy," said Marisa. Her voice seemed to be coming from straight ahead, but he couldn't cast through his own shield. "I can just do something like this."

And he felt his legs lock together. She'd had someone sneak behind to outflank him. He tried to spin around and cast another shield, but his wand was torn from his grip before he could react.

"Good work, Daphne," said Marisa with a grin. "Petrificus Totalus!"

Leo dodged, but just barely. He knew his luck wouldn't hold for that long without a wand or the full use of his legs, and sure enough Marisa's next spell connected.