I was fairly certain that the worst that could happen would be someone in the store instantly realizing that I was some kind of superhuman superfreak, kidnapping me, locking me in a dungeon, and experimenting on me for the rest of my life.

  I didn’t say any of that, though. Instead I shrugged and tried for a smile.

  “Come on.” Izzy pushed the door open, jangling a wind chime on the other side. I followed her in.

  Inside, the shop was quite small. Cabinets and shelves lined every wall, all of them packed tightly with crystals and necklaces, bracelets, and animal ornaments that looked as if they’d come from every country in the world.

  The shopkeeper was tall and wiry, with glasses perched so far down his nose I was surprised they stayed on. He was sitting on a stool behind the front counter, muttering to himself as he shuffled through paperwork. “Now, then, where did I put the . . . ? Ah, hmm, it was here before, and now it’s . . . hmm. Well, I never . . .”

  I coughed gently. The man looked up. He pushed his glasses up his nose and squinted. Looking from me to Izzy and back again, he nodded briskly.

  “Yes?” he said. “Can I help you?”

  Which was when I realized that we hadn’t actually discussed what we were going to do once we got here. We stared silently back at him for a moment. Then I pulled myself together. If I didn’t want him to get suspicious of me, it was probably a good idea to stop acting weird.

  “We were wondering if you have any crystals we could look at.” Great. It wasn’t exactly hard to see that he had an entire shop full of crystals.

  The man opened his arms to encompass the shop. “One or two,” he said.

  “Rose quartz, in particular,” I went on, holding my breath. Why did I say that? He was bound to know why we were here now!

  “Our most popular crystal,” he drawled.

  “Really?” Izzy stepped forward. “A friend of ours bought some from here recently.”

  The man seemed to be stifling a yawn as he continued to shuffle papers. “I’m not surprised. Rose quartz looks pretty and, you know, roses, romance, and all that.”

  “Maybe you’d remember our friend?” Izzy continued.

  “I probably won’t, actually,” the man replied. “The number of customers I get in here, there’s no way I can keep track of them all.”

  I looked around the empty shop. Seriously?

  He stopped what he was doing and looked up. “What does this person look like?” he asked.

  “Well, she’s tall with a smiley face. She usually has her hair tied back and it’s kind of long and dreadlocky,” I said.

  The man frowned and went back to his paperwork.

  “And she wears odd clothes.”

  He looked up. “Oh, hold on a second. I think I might remember her. She was wearing a long yellow cardigan with a kilt with a pair of green tights.”

  That sounded like Nancy. In fact, I was sure of it. I knew the cardigan he meant. It also had pink flowers on it, but I didn’t point that out.

  “That’s her!” I said.

  “Came in twice, actually,” the man went on. “First time on her own, then she came back the next day with a man.”

  With a man? I didn’t know Nancy had a boyfriend. I made a mental note to find out more the next time she came for dinner.

  “In fact, I couldn’t tell you much about her, but I remember the man very clearly,” the shopkeeper continued. “We had a long conversation about the crystals. He wanted to know all about which ones I had, where they came from, who my suppliers were — all sorts of things. He was a very good customer. The kind you want to look after. He bought a huge boxful of crystals. Said he wanted one of every single type that I had. Paid cash as well.” He shuffled through his paperwork again. “In fact, now that I think about it, he was particularly interested in the rose quartz.”

  My heart leaped into my mouth. I tried to squeeze a few words around it. “Did he say where he was from?” I asked in a squeak.

  The shopkeeper frowned again. “Actually, he left his business card.” He pulled out a card from underneath a pile of receipts and waved it vaguely at us before dropping it back on the pile. I couldn’t see what it said.

  Izzy was peering at the card. She reached inside her bag and pulled out her notebook and pen. Then she glanced at me and gave me a quick nod. I knew what she was thinking. We needed this man’s details. He might be our next clue. Someone showing that much interest in the rose quartz, and knowing Nancy — sure, it might all just be a coincidence, but right now it was the best lead we had.

  I pretended to be interested in a huge wooden bird hanging from the ceiling on the other side of the shop. “I wonder if you could tell me about this,” I asked, pointing at it.

  The man’s eyes brightened. “Ah, the eagle mobile. Now, this is a very special bird,” he said, coming out from behind the counter and leading me across the shop. I followed him to the eagle and watched, feigning fascination, as he pulled on a hidden cord that lifted the bird’s wings. Actually, it was very pretty. The way the wings rose and fell was so lifelike, it mesmerized me for a moment.

  Then Izzy coughed and I remembered our mission. I glanced across the shop to see her putting her pen and notebook away in her bag. She must have noted down the necessary information.

  “Well, thank you for your time,” I said to the man. “It’s a lovely shop and we’ll come back again.”

  “Not buying anything?” he asked.

  I felt guilty. Despite what he’d said, I got the feeling he hardly ever had any customers. I glanced at a basket full of random stones and crystals next to the register. It had a sign above it saying, SALE. EVERY ITEM IN THIS BASKET $2.50.

  I rummaged around the basket, looking for something I liked. A couple of things caught my eye. A stone that reminded me of a beautiful pebble I’d found on vacation on a beach when I was about seven. It was bright turquoise with black squiggly lines running all over it. Another stone looked a bit like a Life Saver — white with gray splodges and a perfect hole in the center. The shopkeeper said it was called howlite.

  “I’ll take these, please,” I said, pulling my purse out of my pocket. I handed him a five-dollar bill. Bye-bye, allowance.

  He wrapped them both in tissue paper and stuck a label on them before handing them back to me.

  I thanked the man and turned toward the door. It was time to get out of there.

  We huddled in a café in Memorial Square with a couple of hot chocolates and studied the details that Izzy had scribbled down. There was an address and a phone number. The number was local; I didn’t recognize the address: 33 Albany Road.

  Izzy was busy tapping on her phone. After a minute, she held it up to show me the screen. There was a picture of a map with an X in the middle of it and Albany Road above it. At the bottom of the screen, it gave us various options for getting there. Six minutes by public transportation. Twenty-two minutes’ walk.

  We looked at each other. “What do you want to do?” Izzy asked.

  My stomach suddenly seemed to be playing jump rope. We couldn’t back out now, though. I took a last swig of my hot chocolate, wiped my mouth, and stood up. “Let’s walk,” I said. “I’m running out of money.”

  We discussed our next move as we made our way to Albany Road.

  “So, what do we do when we get to this address?” Izzy asked.

  I looked at her blankly. “Um,” I said. “I don’t really know.” I thought about it. “Do we have his name?”

  Izzy shook her head. “I think it was on the other side of the card, but I didn’t dare turn it over in case the shopkeeper saw me and got angry with us.”

  I walked in silence for a minute as I thought a bit more.

  “You’re sure you don’t want to just ask Nancy about this?” Izzy asked.

  “Yes, I’m sure,” I said quickly. Nancy had bought the necklace, but the shopkeeper had told us it was the man she’d brought in who had been most interested — particularly in the rose quartz. Plus, ch
ecking out some stranger whom I’d never met felt preferable to asking someone who was practically an aunt if she’d secretly set me up with something completely freaky and weird. “Let’s stick to the mystery man,” I said.

  “Do you think he’s going to be our guy?” Izzy asked. “Do you think he’ll know what the crystal does?”

  “No idea. But after what the man in the shop said, he seems like the best option.”

  Izzy smiled. “I hope so,” she said.

  The jump rope flipped around in my stomach. “Yeah,” I said, trying to ignore the worried question marks spinning with it. “Me too.”

  Albany Road was a short cul-de-sac lined with small businesses. A few of them had names on them, like Evans Embroidery and Peters & Sons Fishing Equipment. Most were unnamed and looked anonymous and dark. All of them were closed and locked, some with shutters over the windows. The street felt silent and empty. And a little creepy.

  We made our way down the road, glancing up at the doors to check the numbers. Number thirty-three was right at the end. This one had shutters, too — only these were open. It looked like someone was there.

  Which was when I had a thought. I grabbed Izzy’s arm. “Wait,” I said. I nodded toward an alleyway between a couple of the buildings.

  Izzy followed me into the alley. “What’s up? You’re not backing out?”

  I shook my head. “Not at all. But we can’t go over there without a plan. Come on, Izzy. When do you ever do anything without a plan?”

  Izzy scrunched up her nose and fiddled with her glasses — orange with purple flecks in them today, to match her orange bag with purple writing. “You’re right,” she said. “So what do you suggest?”

  I breathed out hard. “I think you need to go in there on your own,” I said.

  “You are backing out!”

  “I’m not!”

  “But you said — ”

  “I’ll be with you,” I interrupted. “But he won’t know about it.”

  Izzy stared at me for a moment, then she smiled as she realized what I was getting at. “Because you’ll be invisible!”

  “It’s the only way we’ll actually find out anything,” I told her. “What were we thinking we’d say? ‘Oh, hi there. I don’t suppose you’ve come across some crystals that make certain people turn invisible, have you? No? OK, sorry to have bothered you’? I mean, we’ll never find out much by talking to him.”

  “You’re going to go inside?”

  I nodded. “You go to the door and distract him. I’ll sneak in, have a look around, see if there’s anything suspicious.”

  “Got it.”

  “Just don’t go off and leave me, OK?”

  “ ’Course I won’t go off and leave you. We’re in this together, aren’t we?”

  “Hundred percent,” I said. I decided not to point out that Izzy wasn’t the one who had to sneak invisibly into a mysterious building and creep around trying to find out what a scary stranger was up to. It wasn’t her fault I was the only superfreak around here.

  “Ready?” Izzy asked.

  I looked around. The alleyway was deserted.

  “As I’ll ever be,” I replied. I closed my eyes, cleared a section of my mind, and turned myself invisible.

  “OK, let’s go,” I said, and we walked up to number thirty-three.

  I stood back as Izzy pressed the doorbell. And then I held my breath while we waited to see who would come to the door.

  “Yes?” A man stood in the doorway and looked at Izzy. He was small and scruffy, his shirt half hanging out of baggy corduroys, a tie loosely done up, a pair of thick black-rimmed glasses halfway down his nose.

  “Can I help you?” he asked. He wasn’t exactly unfriendly — more impatient, as though we’d disturbed him from something important and he wanted to dispense with us and get back to it as quickly as he could.

  He was standing right in the middle of the doorway. There was barely any space to see behind him, let alone squeeze past without him knowing. I could just about see a small and very sterile-looking hallway with a door leading into another room beyond.

  What was in that room?

  Izzy smiled innocently at the man. “I . . . er, I’m really sorry to bother you,” she said. “I’m looking for number twenty-three.”

  “This is thirty-three,” the man replied sharply.

  “Oh, sorry, my mistake,” Izzy replied as the man went to close the door.

  I nudged her in the ribs to let her know I was still outside with her.

  Izzy leaned forward. “Wait!” she said.

  The man paused and looked at her quizzically.

  “I — I mean, please,” Izzy faltered, “I know that this is thirty-three. Just, well, I’m a bit lost, and I don’t know where to find the one I’m looking for.”

  Finally, the man took a step out of his doorway. “It’s that way,” he said, pointing down the road.

  I tried to squeeze past him, but there wasn’t enough space without bumping into him — and completely giving away the fact that there was an invisible person standing outside his office was the last thing I wanted to do.

  “Sorry, which one is it exactly?” Izzy asked. “Can you show me the exact one?”

  The man sighed, but he took another step away from his door. “It’s five doors down. The one that’s set back,” he said.

  I didn’t hear Izzy’s reply. I was too busy sneaking inside and getting away from the man before he walked into me and the game was up.

  A moment later, the door had closed, the man was heading back inside, and our investigation had well and truly begun.

  The first thing I thought as I looked in through a glass door from the hallway was that it reminded me a bit of the chemistry lab at school. The second thing I thought was that, actually, it was nothing like the chemistry lab at school.

  How it was similar to a chemistry lab: It was filled with scientific equipment and desks. A couple of long Formica tables ran along one side of the room, each with a tall black swivel chair tucked in beside it. Above the desks ran a long shelf, packed with jars, bottles, tubes, and boxes, each with a neatly written label. Each desk had a computer and a load of paperwork. The first desk was arranged neatly with a pile of books, a tray of folders, and a desk planner. The other was covered in a heap of notebooks and papers that were arranged in the kind of mess that possibly made sense to the person who owned them but looked like an amateur burglary had taken place to anyone else.

  Across the other side of the room there was one long work surface. On it stood a huge microscope, surrounded by various racks with different size test tubes propped up in them. Some of the tubes were empty; others had different sorts of liquid in them. It was hard to tell what the liquids could have been: some were clear, others colored. There was a purple one, a pink one, a deep blue, a yellow, and a green.

  So far, a chemistry lab.

  How it was different from a chemistry lab: To start with, as the man stepped toward the glass door into the main area, the door slid open with a soft whshhhhh noise that sounded a bit like the spaceship doors on Star Trek and not at all like the door to our chemistry lab. I quickly stepped through behind him and looked back as the door closed with another whshhhhh followed by a soft clthnnnk.

  My heart did a tiny clthnnnk itself as I discovered that I was now hermetically sealed into a lab that I was gradually realizing looked like a cross between a high-tech experimentation center and a chemistry classroom from a hundred years in the future.

  Bright lights shone down from the ceiling so fiercely that I felt almost pinned to the floor by them. White walls, white ceiling — everything was spotless and clinical.

  Machines beeped and whirred and clicked and buzzed all around me. Just down from the microscope and test tubes was a metal box with orange buttons and red lights blinking above. Next to that sat a bright-blue box with a silver tube running from it up to a white tray on a high shelf. Beyond that, another machine bleeped every thirty seconds. Then there wa
s something that looked like a metal bowl, but it had a digital display on it with numbers that flashed up in pink every few seconds.

  There was only one tiny window at the far end of the room: small, high up, and frosted so no one could see in.

  What on earth was this place?

  The man put on a pair of plastic goggles and took up from where we had presumably disturbed him, studying liquids in tubes and scribbling notes.

  I tiptoed past him and made my way to the far end of the lab. I tried to read some of the notes. They were computer printouts adorned with additions handwritten in multiple colors.

  Sentences were crossed out and written over. Footnotes with asterisks and hashtags littered the margins. Equations that would have made my math teacher faint were randomly scattered in between barely legible notes.

  None of it meant the slightest thing to me — until I noticed a large white plastic box at the back of the desk.

  It was full of crystals. Piles of them, lying in groups.

  I swallowed. This was definitely him, then — the man who’d bought a heap of crystals from the same shop where Nancy had bought my necklace!

  But what did all this mean? What did he want with the crystals? What were all the test tubes for? And what on earth was I to make of his notes?

  I kept silent and watched the man work. After a couple of minutes, he left his test tubes and crossed the room to start punching buttons on one of the machines. A moment later, a handheld gadget on the table beeped. He picked it up and read the screen. Still holding it, he moved over to one of the computers. I silently dodged out of his way as he came right past me. Glancing at the screen of the gadget in his hand, he started typing into his computer.

  I stood behind him, holding my breath, and watched as he typed. He was muttering to himself, but I couldn’t make out what he was saying.

  It looked like he was inputting data into a spreadsheet — numbers and words. I peered at the screen, and a moment later, I had to bite my finger to stop myself from yelping out loud.

  Among all the gobbledygook, three words had jumped out at me as if they were written in bright-red capitals and underlined three times: ROSE QUARTZ: INVISIBLE?