The atmosphere at Grimmauld Place was, as always, sombre. Since Mr Weasley would spend most of his time out at work or visiting his wife, who was still unconscious, Dumbledore had chosen Lupin to take care of the children full-time.

After everybody had arrived, unpacked and lunched, Lupin, still at the lunch table, explained the delicate situation to the children. "Akhmatov was a spy for Durmstrang in Hogwarts," he began.

"What?" asked Ron, astonished.

"Oh, I knew it!" said Hermione. "He was always walking around, taking notes. His behaviour was very strange."

"Yes, Hermione, I would have been surprised if you, attentive young woman that you are, hadn't noticed it. The Headmaster noticed it too, and called him for a talk. After a long chat, the Headmaster let him proceed with his... work."

"How come?" asked Ginny. "Was Akhmatov a double agent?"

"Not exactly. Dumbledore always wanted a closer link to the other schools of magic. So, he gave Akhmatov permission to pass along information to his superiors. You know, the current Durmstrang Headmaster and the majority of his staff don't support Voldemort. They are amenable to a deal with us."

"These political and intelligence matters always confuse me," Ron complained.

"The problem is that a small group inside Durmstrang - led by Karkaroff, who had been in hiding since Voldemort's return - had made a deal with Voldemort without their Headmaster's knowledge. And after being informed about the role that Akhmatov played in Hogwarts, they kidnapped him during the holidays and sent him back under Imperius."

"Bloody hell!" Ron exclaimed.

"Where is Snape?" Harry managed to ask, finally.

Lupin gazed at Harry gravely. "Soon after Akhmatov's disappearance, Professor Snape was called by Voldemort. When he returned, he told us that Akhmatov, under Imperius, installed a magical object in Hogwarts, a magical 'trojan horse', of devastatingly destructive power named Veneficus Trojanus, which gradually destroys all the defences of the building where it is placed. It was manufactured in Durmstrang by their greatest experts in the Dark Arts. In a week, if we don't deactivate it, the Veneficus Trojanus will destroy the castle's defences and Voldemort will invade Hogwarts."

"Oh, no," Harry growled. The four friends exchanged terrified looks.

"Voldemort's original plan was to kill everyone who tried to defend the castle," Lupin proceeded. "Thanks to Professor Snape, the Headmaster found the object in time to send all the students home and prevent any harm being done to them. But we believe Voldemort will still want to conquer the castle, and if Dumbledore stays there, as I think he will, Voldemort will try to kill him."

"Can't that thing be destroyed?" asked Ron, aghast.

"Right now, professors McGonagall, Flitwick, Sprout and Snape are with the Headmaster at Hogwarts, trying to deactivate the Veneficus Trojanus and helping to fortify the castle's defences. Deactivating the Veneficus Trojanus involves great danger, because it destroys everything and everyone that touches it. The Ministry has sent their experts too. Among them, your friend Lescaux, who has sent you his regards," finished Lupin, looking at Hermione.

Hermione flashed a proud and worried smile; Ron grimaced.

A mixed feeling of relief and concern enveloped Harry: Severus was all right, but still in danger. How he longed to be with him right now, and to be able to help him! But he knew Dumbledore wouldn't let him go.

He needed to find a way to escape the Order's vigilance and do something.

~* ~* ~

That evening, the twins Apparated into Grimmauld Place, for a meeting with Harry, Ron and Ginny. However, as Hermione was there too, they decided to tell their plans to her. The six friends went to Harry and Ron's bedroom upstairs, and divided themselves between the two beds - Hermione, Ginny and Harry on Harry's bed, Ron and the twins on Ron's.

At first, Hermione declared herself adamantly against the idea of forming a group parallel to the Order. However, when the twins started to explain their plans, she listened to them attentively.

Fred and George, inspired by the Marauder's Map, had managed to come up with an enchanted parchment that responded to a tiny clothespin, tracking down its location wherever it was taken. That way, if they could fasten the pin to the clothes of a Death Eater, the parchment would display the guy's movements and instantly map his surroundings.

It was an amazing tool. But Hermione still insisted that they should give this new map to the Order.

Harry had kept silent and contemplative during the twins' entire explanation.

"I have an idea," he finally said.

His five friends looked at him.

"Spit it out, Harrykins," said Fred.

"Listen, this is top secret. Don't tell anyone, or I'll hex you."

"Of course! We're very discreet," said George. "And we're together in this, aren't we? There shouldn't be secrets between us."

Harry looked at Fred and George suspiciously. "Okay. Snape's created a potion that alters the Death Eaters's personalities. After drinking it, they can't stand being Death Eaters any more."

"What? Are you sure you're not delirious?" asked Fred.

"Yes. I helped him create this potion."

Hermione's eyes sparkled. "With the Map, we can find the Death Eaters' hiding places and put that potion in their water tank or something like that!" she said.

"Wicked!" Ginny exclaimed.

"That's it," said George. "There's no time to lose. Where's the potion, Harry?"

Harry ran his hand through his hair. "Er... Maybe Snape has one or two flagons, but we're going to need much more than that. We'll have to make more. It won't be easy. I don't even know if I remember all the ingredients... you know I'm not very good in Potions..."

"Can't we put Snape under Imperius?" asked Ron.

"Great idea, Ronniekins!" exclaimed Fred and George at the same time. "We can also fasten the Clique's Map clothespin to his robe."

Hermione shook her head. "That was what I feared. Don't you realise that Snape's important, and that we can't disturb the Order's plans?"

"But Hermione," said Ron, "he'd never agree to help us! The only way is to..."

Ron paled. At that precise moment, a dark figure Portkeyed into the middle of the bedroom, between the beds, holding a ladle.

"Very well, gentlemen, ladies. Who will be the first to try?"

Everybody shrank visibly, except for Harry, who flashed a big smile and needed all his self-control not to throw himself into Snape's arms.

Snape turned around very slowly, glaring at each and every one of them, paralysing them one by one with his Basilisk's look.

Hermione stood up. "Professor, we trust you, and we're not going to attack you. Right, friends?"

"Sure," said Fred and George.

"Do you have permission to Portkey here?" asked Ron.

"That's none of your business," Snape replied.

"How did you find out?" asked Harry.

"Let's say that I have my own sources, Mr Potter."

Harry frowned. Suddenly, shifting his eyes, he stared at Phineas Nigellus's portrait and found a strange look of curiosity and guilt in the former Headmaster of Hogwarts's eyes.

"Ah... I know. I should've known," said Harry. "The good, old Slytherin loyalty."

No one besides Snape, Harry and Phineas understood anything. The whole situation was becoming surreal.

"Snape, our plan is good," said Fred.

"Notwithstanding, you need the old and greasy bat's help to accomplish it," Snape hissed between gritted teeth.

"Let's forget our differences, in the name of the cause," said George, trying to keep serious.

"Let's say that I am amenable to cooperation... as long as I am the one to call the shots here," replied Snape.

Fred and George exchanged discouraged looks.

"Name your terms," said Fred.

"First of all, Harry Potter will not take part directly in any of the actions."

Harry punched the mattress, exasperated. Hermione held his arm, as if to calm him.

"We agree," said the twins in unison.

Harry crossed his arms, furious. Bloody traitors.

"However, there are other conditions," said Snape, and proceeded to relate precisely how the plan should be executed.