The tracking spell led us to the far eastern edge of the magical district. Since we'd only been a few minutes behind the guy when we realized we could use it, it had changed direction as we walked, my mother's amulet that I'd tied the sympathy components to periodically changing the direction it was tugging toward the wizard we were following.

In the haphazard labyrinth of buildings, we were losing ground just adjusting to get around buildings that were in the way, guessing how he'd gone around them based on where it had been tugging before. So when it started tugging down, we started looking for a sewer grate or basement. It would have helped if anyone was a local. Finally, as the sun was starting to set and the tracking spell had about used up the material available, Alexis found a concealed basement door next to a building, and we went down.

The tunnel beneath ran further east, and we must have been leaving the magical part of Kheima and into the muggle city, a large suburb north of Cairo proper. "I'm tapped out, guys," I said, as the charm finally broke.

"I think we found what we needed," Michael said as we entered a larger space, ready for a fight. We were having to use light charms to see, so we couldn't exactly sneak up on anyone. "Looks like a staging area?"

The underground room wasn't that big, but had transfigured stone countertops installed against the earthen walls, and venting chimneys running away and toward the surface. Michael had clearly noticed the square spots of absent dust on the floor near a large doorway on the opposite side of the room, but didn't understand the significance of the rest of the furniture. "It looks like a potions lab that has had its apparati removed," Percy seconded aloud what I'd been thinking.

"So they were brewing something, packing it up, and then taking it into the mundane parts of the city," Michael figured. "There's still dust in the air like they were here for the last load this afternoon."

"Do we know any diagnostic charms to figure out what they were brewing?" Penny asked Percy and Alexis.

"Don't bother," I told them, standing near the brewing station and sniffing. "I recognize the smell. Mathilda just bought me new components to make it."

"Erumpent potion!" she exclaimed.

Michael raised a questioning eyebrow and I explained, "Magical explosive. Think of it like nitroglycerine. More stable, bigger boom…"

"And I bet it doesn't leave a chemical residue or use precursors the government could track?" the swordsman guessed. "Same or denser form factor as nitro?" I nodded and he grimaced, "If all the crates it looks like were in here were full… this could be a tremendous amount of explosive."

"The merchants at the preserve!" Mathilda said. "They told me I was lucky to catch them when they had some fresh. There was a lot of demand for their supply in the city! They hadn't been able to keep it in stock!"

"Can you track the supply that way? See who was buying it?" Michael asked.

"I can ask my brother," Percy nodded. "Though wizarding vendors do not really keep extensive records unless legally required. Perhaps we could–"

"Lights!" I hissed, cutting him off. "Someone's coming." I'd hopefully heard the steps before the new arrival heard us.

We quickly moved back to the side of the room and doused our lights, refocusing eyes making out another light coming from the hallway down which they'd presumably taken the crates. Probably the same guy we'd been following entered the room, his wand lit and held high. Before he even registered the illumination falling on the seven people in the room, he'd been hit with three stunners.

I needed to look into whether it was dangerous to do that before we killed someone by all stunning them at once.

Fortunately, the guy didn't have any backup. We took his wand, tied him up, and revived him. We'd agreed to let Michael take the lead while we all stood behind the guy: if, for some reason, he went to the aurors, we had a lot more to lose than the swordsman did since he could get out via plane while we had to take a state-controlled portkey.

"I want to know about the erumpent potions. Talk," Michael ordered him. Something about his command seemed designed to speak to the guy's very soul. It wasn't a magical compulsion, exactly, but just like he was the kind of guy who had the right to make you confess.

"You aren't an auror, American," the guy grated out. "But it was just a job. They provided the materials, I made the potions and delivered them. Easy."

"And when they're used?" Michael chided the man.

"On muggles," the guy shrugged, or at least as much as he could thoroughly trussed up.

"Why does an elf want to use explosions on muggles?"

"Something about drawing attention. I don't know. They pay me to brew, not to care about politics." He looked around what he could see of the room. "It's gone, anyway. I'm not sure where. I already put it on the train. I should have ridden with it, I guess."

"How much did you make?"

"About four hundred liters. It took quite some time." The guy seemed pleased with himself.

Michael signaled, and I stunned the guy again. "This is bad?" he asked

I nodded. "Based on how big those crates probably were, and if I'm visualizing soda bottles right… could be, what, a dozen heavy crates? I've never made more than a pint of the stuff, but an ounce is enough to blow a big guy off his feet. Each crate is probably like a big pack of dynamite?"

"I don't know enough about demolitions to judge what you could do with that much," Michael thought out loud. I shrugged because I didn't either. "But it sounds really bad."

"Can we just… turn him over to the aurors?" Percy asked. "At the very least he was muggle-baiting. That much of the potion is probably illegal, too."

"If you don't think they're corrupt here, okay," Michael nodded. "I think I can talk to Nakht about getting him picked up with no questions asked. But I've never known the wizarding police to really care about what happens to ordinary people."

I had a hard time disagreeing with him.

It wasn't easy to go back to vacation after that. We traded contact information with Michael, in case any of us learned something. And we had to fess up to the chaperones more or less what we'd been up to. We didn't dwell on the particulars busting up Necropolis, so much as just seeing Michael and helping him track an illegal potions lab.

We always had a real grown up with us from then on. Molly Weasley, in particular, had a very scathing tirade about Percy putting his life in danger instead of just calling the aurors. She wanted to know why we even bothered going on vacation instead of walking deep into Knockturn Alley at home and picking a fight.

The second week of August, the Grangers joined up, flying in from France. With them in tow, it was a lot easier to see the muggle side of the city, which the adults felt like might be safer in case more Death Eater bounty hunters were in the area. Word had gotten to the Longbottoms that the Egyptian aurors had tracked down several crates of the illegal erumpent potion through various detection spells and removed it to safety. So maybe everything was completely fine, we'd done a good thing, and leaving it up to the proper authorities had paid off.

Of course, my life is rarely that easy. Michael got word to us that he was worried that he needed to be in downtown Cairo, so we should definitely stay away and let him handle it. Naturally, Mathilda insisted that meant we needed to be there. And that's how the original crew of the six of us wound up deciding that we wanted to learn about the Egyptian parliament and check out the other government buildings downtown on the last Thursday of our trip, August 19th. Naturally, Arthur Weasley was happy to chaperone on a trip to learn about the muggle equivalent of the Ministry, and Alice Longbottom tagged along just in case the girls wanted to break off from the guys to do something. Fortunately, it seemed super boring to all the younger kids who insisted on going to see the pyramids, safely far away. Bill was apparently "pyramid sitting" for one of his fellow curse breakers that week, so could get the kids in to see some of the hidden chambers that weren't on the muggle tours.

It took most of the day to finally spot Michael. He was easy to notice because he was running. He looked frantic, chasing after a motorcade of black cars leaving Tahrir square and turning east past us where we were looking around the campus of the American University (it was nice to talk to more people who wanted to speak English for a bit).

Even in traffic, cars are faster than a running middle-aged man. We were closer, but it took a few vital seconds for me to realize what was going on. By the time I realized he was trying to stop the cars, it didn't matter. They were still a couple hundred yards from us, but in the midst of possibly hundreds of other tourists between the university and a muggle government building. I saw what Michael had seen, from his better vantage point: suspicious construction in the street at a corner that could intercept traffic to the Ministry of the Interior from multiple directions. We were too late.

Boom.