"I— I mean, I don't know anything about Gillyweed!" Neville stammered. "Honest!"
"Come now, Longbottom," Oleandra said soothingly. "Lying ill befits you— and you shouldn't be ashamed of helping your friends. Actually, I thought it was rather brave of you to go behind Professor Snape's back for a good cause."
Neville cringed a little when he heard the words 'Professor Snape,' but otherwise, he reacted favourably to Oleandra's praise, which meant that she had hit the nail on the head. So, Harry had sent Neville to do his dirty work; though that didn't explain how Neville had managed to defeat Professor Snape's enchantments— because, of course, he would have learned his lesson from the thefts two years ago, and not left his cupboard undefended.
"Y-You really think so?" said Neville sheepishly. "My gran always used to tell me I could achieve anything if I just believed in myself. I s'pose… I just took a chance, and I guess it paid off!"
"Did Harry happen to say what he needed the Boomslang skin for?" Oleandra casually asked.
"H-huh?" Neville said. "Harry never asked me for anything— and I didn't steal any Boomslang skin…"
Well, now Oleandra was just confused. Harry wasn't the type to ask for help, even from his friends, so she supposed that Neville might have overheard Harry talking about needing to breathe underwater and about something that required Boomslang skin. But if Neville hadn't stolen the skin, then who had?
Unfortunately, Oleandra didn't get the opportunity to ask for more details, as Professor Snape had just finished threatening Harry with Veritaserum, the most potent Truth Potion in existence, and he was back to making his rounds of the class.
Not wanting to be overheard talking about stealing from his cupboard, Oleandra and Neville both clammed up. It was a good thing that Neville always acted this scared of Professor Snape, because otherwise, the Potions teacher would have immediately found his behaviour suspicious.
A few minutes later, there was a knock at the door ("enter!" said Professor Snape), and Professor Karkaroff entered the classroom, making a beeline to Professor Snape's desk.
"We need to talk, Severus," said Professor Karkaroff stiffly.
"Not now, Karkaroff," muttered Professor Snape. "After my lesson—"
"You've been avoiding me, Severus," Professor Karkaroff insisted. "But there's nowhere to run—"
If it had been before Ron and Hermione had told her that Karkaroff had used to be Death Eater, she would have thought this a simple lover's quarrel, but now, she couldn't help imagining that something sinister was afoot.
"After the lesson," Snape snapped, and that was the end of that…
Or not. Even though he had very subtly been invited to leave, Karkaroff instead elected to hover behind Professor Snape's desk in a very distracting manner until the end of the lesson. Just before the bell rang, Oleandra heard a crash behind her; somebody had dropped a glass bottle.
It was Harry; he had very likely caused a mess on purpose in order to stay behind to listen. Well, it just happened that Oleandra was very curious to know about the two men's discussion, so she decided to hang around outside the class and confront Harry about what he'd heard after the fact.
"You two head on back without me," Oleandra told Daphne and Tracey when class ended two minutes later as they crossed the doorway back to the dungeons.
Oleandra leaned against the wall and waited for all the other students to leave, before putting her ear to the closed door. Muffled voices; Professor Snape and Karkaroff were talking, but she couldn't tell quite what about. If only she knew magic to eavesdrop on people…
"Can you peek inside and tell me what's going on?" Oleandra asked Viviane, who shook her head.
"I'm not a ghost, remember?" she said. "I can only see what you see and hear what you hear."
Suddenly, the voices coming from the other side of the wooden door turned into shouts, and she heard someone walking rapidly towards the exit. Oleandra rapidly jumped to the side to avoid being knocked over by the door swinging open.
"What are you looking at?" Karkaroff spat at Oleandra.
She had activated her Mystic Eyes and was staring at the dark gloomy aura gathered around his left forearm, which was visible to her even through his thick sleeves.
"What's that on your forearm?" Oleandra said innocently, pointing to his left arm.
Karkaroff blanched and instinctively seized his left forearm with his right hand, immediately checking to see if it was properly covered by his robes. And indeed, it was.
"Nothing, you little cretin," he hissed at her, before storming off. Wow, rude.
Moments later, Harry also emerged from the Potions classroom in a rush, clutching his bag in his arms.
"Hang on a moment, Hero!" Oleandra called out to him. "What did you hear in there?"
"Not in front of Snape's classroom!" Harry shot back. "There's a Hogsmeade visit tomorrow— meet me on the outskirts of the village, past Dervish and Banges, at half past one. There's someone who wants to talk with you; bring your sister if you want, but it'd be best if you came alone."
And with that mystifying response, Harry sped off back up the stairs which led out of the dungeon, leaving Oleandra with more questions than answers. Not wanting to stay overlong near Professor Snape's classroom, Oleandra also made her way back to her own common room, where Daphne and Tracey were awaiting her.
After Oleandra recounted everything that she had witnessed, Daphne shook your head.
"You've got enough on your plate as it is," she said crossly, "without getting mixed up in other people's problems. You should focus your energies on preparing for the third task, instead of going gallivanting through the countryside."
"So that's a no for you, then?" Oleandra asked.
"I for one, have a Bloodline Atavism Potion to complete," said Daphne. "I need every free moment I can get, so that's a no."
"I wonder what this could all be about?" Tracey sniffed. "Harry knows I'm friends with you, so why can Daphne come, but not me?"