"We're contacting Ron and Harry right now," John said when he'd recovered enough to speak.

For once, Sherlock didn't argue. They went straight to the Owlery, and within half an hour, Sherlock was attaching a letter to his tawny owl's leg. He had charmed the envelope to say URGENT in flashing red letters.

"What do we do until they get here?" John asked as they watched the owl fly off.

"I am going to learn everything I can about James Moriarty, and you are going to go back to your dormitory and rest," said Sherlock.

John snorted. "Not bloody likely."

Sherlock frowned. "Actually, you're right," he said. "Moriarty will be expecting that. You'd better take my bed in Ravenclaw Tower—or better yet, go back to the Room of Requirement. If you ask it to protect you, Moriarty won't be able to get back in."

"That's not what I meant!" said John. "I'm not quitting just because I got Stunned for a second."

"No, you're quitting because Moriarty is out to get you. Or did you miss his parting words?"

Sherlock's face was hidden in shadow, but in the moonlight, John could see the boy's hands clutching the window ledge. He had never been more tense.

"You're really worried about me, aren't you?" said John, oddly touched. Sherlock didn't respond.

John sighed. "I'm not letting you go after Moriarty on your own," he said. "He threatened us both, remember? We do this together, or not at all."

"Fine," said Sherlock. "But you'll need sleep first."

"So will you."

"I don't need as much sleep as other people."

They argued about the logic of this statement all the way to Ravenclaw Tower.

O0O0O

The next morning, Professor Longbottom caught John as he was entering the Great Hall and led him to an unused classroom. Harry, Ron, and Sherlock were already there.

"Do you have any proof?" Harry asked when the boys had finished their story.

"Nothing concrete," Sherlock admitted. "But it all fits. He's the only person who knew Molly was going to be in the Slytherin dormitory. Find out what class he had at that time—I guarantee you he didn't turn up."

"And Sherlock and I can testify against him," John added. "We both heard him confess everything."

"I believe you," said Harry. "But the Ministry of Magic isn't going to throw a twelve-year-old in Azkaban on the word of two kids."

"What do you have to say about this, Neville?" Ron asked Professor Longbottom. "You must know the Moriarty kid."

"I can testify that he's frighteningly intelligent and a bit creepy," said Longbottom, "but that's all."

"And that's not enough," said Harry. "We need hard evidence, or this will all be a waste of time."

An idea popped into John's head—a wild, terrifying idea. He spoke up before he had a chance to think twice about it.

"What if you saw him poison someone with your own eyes?"

The others looked at him, startled.

"That would do, obviously," Ron said after a moment. "But he's not going to try anything right in front of us, is he?"

"Maybe you could be hiding nearby," said John. "All you'd need is the right bait."

Sherlock sprang to his feet.

"John, no!" he shouted. "It's too dangerous!"

Of course, his friend had deduced exactly what he was thinking.

"I'll be fine," said John. "Moriarty can't hurt me too badly with these two nearby."

Longbottom looked nearly as worried as Sherlock, but Ron looked more impressed than anything else. Harry's expression was the hardest to read.

"I appreciate your vote of confidence, John," he said, "but this could still be dangerous. Are you sure you want to take such a risk?"

The image of Molly lying unconscious on the floor of the Slytherin common room came unbidden into John's mind.

"Yes," he said. "I'm sure."

O0O0O

John felt less nervous approaching Moriarty than he had approaching Irene Adler. He knew that was absurd—the worst Irene could be accused of was greed, whereas Moriarty had nearly killed three people. But his outrage seemed to leave no room for any other emotion. The languid smile Moriarty gave him as he walked up to the Slytherin table only made him angrier.

"May I help you with something?" Moriarty asked.

"It's all over." John spoke quietly so as not to be overheard. "I sent an owl to Harry Potter, and he agreed to meet with me tonight. I'm going to tell him everything."

Moriarty's smile only widened.

"Oh, really?" he said, not bothering to keep his voice down. "Thank you for warning me. That's very…fair of you." He turned back to his lunch.

That's it? thought John. No threats, no theatrics, no monologue about how he would get his revenge? Not even another scathing remark about John being Sherlock's dog?

After standing there awkwardly for several seconds, John went back to the Hufflepuff table. A trap had just been set, but he wasn't sure who was the hunter and who was the prey.

O0O0O

The following eight hours were the most stressful of John's life. Every second, he was expecting Moriarty to leap out of the shadows with his poisoned rag. Every object he had reason to touch was suspect; he didn't eat a bite at dinner.

Every once in a while, he would catch a glimpse of Ron or Sherlock or Professor Longbottom trailing him. Harry, he supposed, was hiding under his Invisibility Cloak. This made John feel a bit safer, but he couldn't help wishing his allies were a bit closer. How much damage could Moriarty inflict before they got within Stunning distance?

Don't whinge, he told himself sternly. This was your idea.

To make matters worse, Sherlock showed up at dinner looking like he'd run headlong into the Whomping Willow. John all but sprinted to the Ravenclaw table.

"What happened?" he asked frantically. "Was it Moriarty? Did he—"

"Of course not," Sherlock cut in. "Moriarty doesn't fight with his fists. It was Sebastian Moran. He cornered me in the loo. Don't worry," he added at the look on John's face. "For once, his minions weren't there to hold me down, so I got away before he could do much damage."

John's fists clenched. On any other day, he would have set off to find Moran without another word, but they had bigger problems at the moment.

"Put some ice on that eye," he told Sherlock before going back to his table.

After dinner, he started walking in the direction of the Astronomy Tower. They had all agreed this was the best route. The tower was somewhat remote from the rest of the castle, which was advantageous for a couple of reasons. It was plausible that Harry would ask John to meet him there, and the long walk gave Moriarty plenty of time to make his move.

John reached the Astronomy Tower without incident. With nothing else to do, he climbed the stairs to the top of the tower and waited.

As the minutes ticked by, John began to worry for an entirely different reason. What if Moriarty didn't turn up? What if he saw right through John? What else could they do?

"I don't think he's coming."

To his eternal shame, John shrieked like a five-year-old girl.

"Oh, sorry!" said the disembodied voice. There was a rustle of fabric, and Harry Potter appeared before him, clutching a silvery cloth that could only be the Invisibility Cloak.

Harry kindly ignored John's jumpiness. "You might as well go back to your dormitory," he sighed. "I'll walk you there, just in case."

They descended the stairs in silence, each lost in their own thoughts. John had never dreamed he could feel so disappointed about not being assaulted.

"Looks like he's not coming," Harry called as they exited the tower. "Best call it a night."

There was no response.

Harry frowned. "Ron? Neville?"

Silence.

Harry pulled John back against the wall. "Something's wrong," he whispered. "Ron and Neville should be here."

"And Sherlock," John whispered back. "I'm sure he came along, whether they told him to or not."

Harry consulted the Marauder's Map and groaned.

"Damn," he said. "Something's definitely happened."

He tilted the map for John to see. Dozens of black dots were congregated around a spot in the dungeons, so many that the names jumbled together and became indecipherable. It looked like ants swarming over a breadcrumb.

John swore under his breath. He could only think of one reason why that many students would be in the corridors at this hour. Without another word, he and Harry began running towards the dungeon.

Sherlock, John thought. He went after Sherlock first. Of course he did. He must have lured him down to the dungeons somehow and…Oh, God, please don't let him be…

Before he had even finished thinking it, the answer to his prayer came bounding around the corner and crashed right into him.

"Argh! John, didn't your mother ever tell you not to run indoors?"

John had never been more relieved to hear himself insulted. "Sherlock! You're okay!"

"For the moment," Sherlock said grimly.

"What do you mean, for the moment? What happened?"

"There's been another poisoning," said Ron, coming up behind Sherlock. Professor Longbottom wasn't far behind.

"Who was attacked this time?" John asked.

The other three looked at each other, as though trying to decide who should break the news. In the end, it was Longbottom who spoke.

"Jim Moriarty."