The next morning, one of the last few days of term, it was so cold that Herbology was cancelled. Some of the Slytherins, stuck in Transfiguration with the Ravenclaws, were rather jealous. Leo didn't particularly mind, though: Transfiguration was very useful and he'd have all the free time he needed soon once the holidays began.
At lunch, the Slytherins were gathered at their table in the Great Hall when the news came: there had been another attack on Justin Finch-Fletchley and a ghost.
"Where does that put your theory that Potter isn't the heir now?" asked Tracey, who had firmly believed that he was ever since the Duelling Club.
"Actually," replied Leo, "it makes it more likely."
"What?"
Leo rolled his eyes, but Marisa was one step ahead of Tracey and began the explanation before Leo could.
"If Potter is the heir, and he has a brain, then he wouldn't have gone after Finch-Fletchley after that incident because he knows that that would make people suspicious of him. We already know that if Potter is the heir, he must have a brain, otherwise he'd be a blood-purist Slytherin. Therefore, Potter is not the heir."
Leo nodded. "Correct. There's just one thing you missed: it could be that Potter realises that this will be our chain of reasoning and so has attacked Finch-Fletchley to draw the suspicion of the actual intelligent people away from us…"
Marisa shot him a look. "Do you really think that's likely?"
"No. But it's a possibility."
Marisa was getting annoyed by Leo's insistence on pursuing the most unlikely scenarios. But this time, she had backup. It was somewhat weird for her to be on the same side as Draco as they, Theo, Tracey and Daphne all verbally attacked Leo.
"How would you all feel if he was the heir and had been doing what I said and you were all wrong?" asked Leo.
"Since that's never going to happen," replied Draco snidely, "it's irrelevant."
Marisa was strongly tempted to bang her head against the table. She had been listening to this sort of thing far too often recently.
"I've been doing a bit of research," said Leo to Marisa on Christmas Day, "and if Potter and co. started brewing in November the Polyjuice should be ready today. Keep on your guard."
Marisa nodded.