"I doubt it's the Fu-Tsang," said Kiki. "Most of them are in jail. The rest are probably too scared of the rats to go back to the tunnels. Three of them did get eaten last time."

"Then who do you think it could be?" asked Luz.

"We don't know," I admitted. "We don't even know how they got inside."

"But we have to find out," Kiki said. "Anyone have any ideas?"

"I have some motion detectors I just made," said Luz. "I was going to use them to keep my sisters from snooping through my workshop, but I guess that can wait. I'll have to make a few more, but it shouldn't take very long."

"When could they be ready?" asked Kiki.

"If I stay up late, I could have everything done by tomorrow. But there's one thing I'm gonna need."

"What?"

"If we want to put the motion detectors in all the right places," said Luz, "I'm going to need the map of the Shadow City."

I shuddered when she said it. All summer, I had taken sole responsibility for protecting the map. After all, there were only two copies left in the world. The first unfinished map was on a disk stolen by Sidonia Galatzina. The second was a single sheet of paper that I usually kept tucked away between the pages of Glimpses of Gotham. There were no other copies, no more computer files. After everything that had happened, the Irregulars couldn't risk letting the final version fall into the wrong hands. I've never claimed to possess psychic powers, but the moment the map was no longer in my possession, I knew we were all in trouble.

THINGS YOU CAN LEARN BY GOING THROUGH THE TRASH.

Several years ago, a mysterious British man began supplying London's journalists with embarrassing stories about the private lives of famous people-and no one could figure out where he'd gotten the information. Many suggested he was hacking into celebrities' computers or staking out their homes with fancy cameras and listening devices. The truth was far... dirtier. All of the scoops came from one low-tech source-the trash.

In the United States, your trash is public property. As soon as you set it out on the curb, anyone is welcome to have a look. It's a treasure trove of information for detectives, journalists, parents, and criminals who have no qualms about picking through your banana peels and used tissues to find what they're after. Just one bag of garbage may reveal the following:

Everything a Crook Needs to Go on a Shopping Spree

Be careful when throwing out any documents that list bank account or credit card numbers unless you're willing to foot the bill for a stranger's Las Vegas vacation or her calls to the psychic hotline.

Your Telephone Numbers (and Who's Been Calling Them)

One cell phone bill will give a snoop a full list of the calls you've made or received for an entire month. So be careful who you talk to-or shred your bill before it hits the Dumpster.

A List of Your Friends, Loved Ones, and Mortal Enemies

Been swapping notes with your friend's crush? Did your grandmother foolishly ignore the advice of the witness protection program and send you a birthday card? Have you been doodling unflattering pictures of your loathsome math teacher? Dump them properly, or be prepared to pay the price.

Your Academic Achievements (or Lack Thereof)

If you're a star student, this may not be your biggest concern. But if your test scores reveal you've been spending way too much time exploring noneducational sites on the Internet, you might want to dispose of the evidence in a discreet manner.

A Menu of Your Favorite Foods

Any outspoken vegetarian who enjoys a secret hamburger from time to time-or health nut who harbors a forbidden love of Twinkies-should keep in mind that one look through her garbage can reveal all of her weaknesses.

Your Bad Habits

You know what they are. Would you care to share them with others?

All the Places You've Been

Countless items in your trash-receipts, shopping bags, airline tickets, surgical dressings-can help someone piece together your activities. Toss them only if you've been on your best behavior.

CHAPTER FOUR.

Attack of the Squirrels

For the first time in weeks, I was tucked into bed at a reasonable hour, but no matter how many pigeons I counted (I wasn't that familiar with sheep), I couldn't fall asleep. Oona was angry, Kiki was worried, squirrels were attacking innocent park-goers, and someone was inside the Shadow City. But worst of all, the map was in Luz's hands-and out of my control.

The next morning, I practically sleepwalked to school. By the start of first period, I had already left my geometry book on the subway, injured my pelvis by walking into a parking meter, and forgotten to turn off my cell phone. Just as I began to drift off in the middle of Mr. Dedly's lecture on Dutch wall construction, it began playing the theme from Jaws. Cell phones were forbidden at the Atalanta School, and I would have rather been caught with a dead body in my locker than a ringing phone in my hand. I winced as every head in the classroom turned toward the purse that was hanging from my chair.

"Out, Ananka," Mr. Dedly bellowed. "Deliver your musical handbag to the principal's office immediately."

A girl named Petra Dubois had the nerve to snicker as I stood up.

"Wonder if Principal Wickham would like to know who wrote your last essay?" I whispered as I passed by her desk, winking when she gasped. Gossip may be petty, but it certainly has its advantages.

"OUT!" Mr. Dedly shouted.

Once I was in the hallway, I quickly ducked into a bathroom and answered the phone.

"This better be somebody's one and only call from jail," I growled.

"It's worse," said the voice on the other side. "Did I get you in trouble?"

"Let's just say I may be looking at a very bleak future. What do you want, Betty?"

"I just heard from Kiki. Luz got mugged on the way to school this morning." There was a brief pause. "By the squirrels."

The idea that Luz Lopez had been the victim of a robbery, particularly one perpetrated by wildlife, was staggering. Her surly disposition usually succeeded in keeping most people and animals at a distance.

"Where?" I asked. "Is she hurt?"

"She's a little scratched up, but she'll survive. She said she was cutting across Morningside Park when three huge squirrels jumped her. A jogger pulled them off, but by that time her backpack was gone."

"The squirrels have moved uptown? How much money did they get?" I asked.

"There wasn't any money, Ananka." Betty was trying to break the news gently.

"No," I moaned.

"Yeah. They got the motion detectors. And the map."

My worst fears had come true. "What's Kiki say?"

"She wants us all to meet at her house after school. We're going to Morningside Park to get the map back."

"Are you kidding?" I asked. "There's no way the squirrels will still be there."

"Kiki said you'd say that. She told me to give you a message."

"What is it?"

"She wants to know if you have a better idea."

"I'll try to think one up on my way to reform school," I huffed and hung up.

The walk to Principal Wickham's office was known as the plank (as in "Jordan was forced to walk the plank yesterday, and nobody's seen her since"). Her door sat at the end of a gloomy hall in a part of the school that most people avoided. It was a well-known fact that, back in the days when the building was a home for wayward children, the office had belonged to a doctor who enjoyed practicing his surgical techniques on hapless delinquents. While I'd always felt a certain fondness for Principal Wickham, there were plenty of Atalanta girls who swore she could be equally cruel.

I knocked at the door before opening it a crack. Principal Wickham was paging through a stack of files, and she looked tiny and old behind her enormous oak desk. Judging by the stories floating around, one might have expected to find the heads of naughty students mounted like hunting trophies on the walls. Instead, dozens of dusty photographs clung to the dingy plaster. In one, a well-known painter posed beside her masterpiece at an exhibition of modern art. Another photo had been snapped at the recent inauguration of New York's first female senator. The rest of the pictures spanned at least four decades, but they all shared two things in common. They each focused on famous women-directors, writers, CEOs, and surgeons. And in each one, hidden somewhere in the background-her face blurry or half concealed by a champagne glass-was Principal Wickham. Even in the black-and-white photos taken in the days when women never left the house without their hats, gloves, and stockings, she looked a hundred years old.

"I had a hunch I'd be seeing you soon, Miss Fishbein," the principal murmured without looking up. "Come in. Make yourself comfortable."

I plopped down in one of the hard leather chairs. While I waited for her to finish her paperwork I stared at a defective smoke bomb that sat on her desk. The fuse was singed, but it hadn't burned.

"So," the principal finally said, laying down her pen and removing her bifocals. When her eyes met mine, I realized that even without her thick glasses she could see things that others couldn't. "What do you make of that?"

"What is it?" I asked in my most innocent voice.

"That is the cause of the disturbance yesterday. I believe you would call it a stink bomb. A particularly effective one, I might add. Whoever made it deserves a suspension from Atalanta and a scholarship to Harvard. I'd ask if you knew anything about it, but I've seen your chemistry grades, Miss Fishbein, and I doubt if you're up to the task."