414 words. For Hogwarts January Writing Month.

The room was instantly filled with a furious uproar, and for one horrifying moment Leo was convinced his plan wasn't going to work, that they'd be so angry they would just attack her anyway. He stood still and waited for the initial shock to pass and silence to resume. Now the Slytherins weren't the united force they'd been just a second before: they were confused, whispering to each other and breaking into smaller groups.

Finally, Draco said loudly, "Why would you lie to us?"

"Technically I never explicitly stated that I was a Mudblood and therefore didn't lie," said Marisa. "I merely allowed you to believe that I was a Mudblood."

"But still… why?"

"Because I wanted to find out who was Slytherin enough to realise that I couldn't possibly be a Mudblood," said Marisa. "Call it a test to see who would be the most useful allies."

"I worked it out as soon as we met, of course," continued Leo, making it up as he went along. "Do you seriously think I would have let myself get this close to her if she was a Mudblood?"

"I – " said Draco, "so – if you're not a Mudblood – "

"Half-blood," said Marisa, "but my parents divorced when I was young. My dad was a wizard but I never saw him after I was about two so I didn't know about magic until I got my Hogwarts letter. And I realised I'd have to learn quickly, so I wanted to find out who I could rely on to help me find my feet."

"You're insane," said Theo.

"Isn't everyone, to some degree?" asked Marisa. "Or do you claim to be a perfectly logical and emotionless machine, like Leo?" She winked at him.

Leo shot her a death glare, not being able to protest without admitting that he did have emotions.

"It is a perfectly sane plan, and what's more it did work. I know who I can rely on – to stab me in the back when I need him most."

"I'll stab you in the back now if you're not careful," said Leo grumpily, but Marisa had achieved her goal. The tension in the room had vanished and everyone began to go about their business.

"Anyone for Exploding Snap?" asked Leo, heading over to his friends, but Daphne shook her head. "Could I just have a word with Marisa first? In private?"

"Sure," said Marisa, and the two girls hurried up to the (empty) second-years' dormitory.