Charlie Thorne and the Last Equation

by Stuart Gibbs

  Instead, she was forced to stare at Einstein’s clue, trying to decipher it.

  She probably would have been doing that anyhow, even if her brother hadn’t threatened her, because the equation was a puzzle created by Einstein himself. How could she possibly resist trying to solve it? But she was irritated by the tactics Dante had used on her. He hadn’t even thought to ask her nicely or offer encouragement. Instead, he had gone right to the threat, like she was an enemy, rather than family.

  She tried to push her anger at Dante aside, not wanting it to cloud her mind, and focused on the clue:

  “What do you have so far?” Dante asked.

  “Nothing,” Charlie said tartly. “You can’t make someone think harder by threatening them, you know. That’s not how thinking works.”

  Dante ignored this. “I’m sure something must have grabbed your attention.”

  Charlie looked back at the clue. “Okay. The last character doesn’t make any sense.”

  “The pi sign?” Milana asked. “What’s wrong with it?”

  “Pi is a very specific number,” Charlie explained. “3.14159 and so on for another trillion numbers.”

  Dante said, “Your mother claims you memorized it to two hundred and fifty places when you were seven.”

  “Three hundred and fifty,” Charlie corrected. “And I was six. The presence of pi is another reason I know this isn’t an equation. Pi is useful if you need to calculate the area of a circle, but it’s an extremely unwieldy result for a complex formula. The chances of this equation being equal to pi has to be a quadrillion to one. . . .”

  “Fine,” Rats said curtly. “What’s your point?”

  Charlie said, “The numerical definition of pi probably isn’t relevant here. But pi is also the letter P in Greek. And since Pandora was a character in Greek mythology, then pi probably stands for ‘Pandora.’ ”

  “Okay,” Dante said, sounding pleased. “That’s something.”

  “Not really,” Charlie replied. “To Einstein, this would have been obvious. Kiddie stuff. All I’ve done is determine what I’m solving for. I haven’t even scratched the surface of the clue.”

  “Then let’s talk about that,” Milana said. “What are you thinking?”

  Charlie looked at her. She liked Milana’s technique much more than Dante’s. Milana seemed concerned about her. Sisterly. Nurturing. Maybe she was just playing good cop to Dante’s bad cop in some sort of routine they’d worked out, but it still made Charlie like her more.

  And yet . . . There was still something that bothered her about how the CIA was handling Pandora. Personally, she had a better plan to protect the equation, but she didn’t want to mention it, because she was sure that Dante and all the others, even Milana, wouldn’t agree with her. Instead, she figured it would be best to do what they asked of her, to be a team player for now, while she waited for the opportunity to make her move.

  Charlie pointed to Einstein’s clue. “I’m going to assume this is a cipher, and your most basic form of cipher is a cryptogram. That’s where one character or group of characters stands for another. This would be the simplest version.” She quickly sketched out a diagram on the pad:

  A

  B

  C

  D

  E

  F

  G

  1

  2

  3

  4

  5

  6

  7

  “Here, A equals 1, B equals 2, C equals 3, and so on, so the word ‘CAB’ would be ‘312.’ ”

  “This is ridiculous,” Rats said suddenly, like he’d been biting his tongue and now couldn’t stay silent anymore. He spoke to Dante as though Charlie weren’t even in the car. “I get that this kid might be some sort of math prodigy, but now you’re gonna let her lecture us on codes?”

  “I know plenty about codes,” Charlie told him coolly.

  “How?” Rats challenged. “Has the CIA trained you to be a specialist in it?”

  “Puzzle magazines,” Charlie said. “Any newsstand has dozens of them. I’ve been solving cryptograms and other ciphers since I was three.”

  “And that qualifies you to tell a bunch of CIA agents what to do?”

  “Charlie has succeeded at everything we’ve asked her to do so far,” Milana said to Rats sharply. “She located this cipher in the first place—and defeated one of the Furies to get it—while you let their leader escape. So I’d really appreciate it if you’d let her speak.”

  Rats fell silent again, although Charlie could see in the rearview mirror that he was seething.

  “Sorry about that,” Milana said to Charlie. “Now, if this was a cryptogram, how would you solve it?”

  Charlie grinned, heartened by her show of support. “I’d start trying to decrypt something by looking for patterns that correspond to the patterns in words. If a pattern showed up with great frequency, I could assume it’s a letter that appears frequently, like E, A, or S in English. Or I could look for keystone words, which have distinct letter patterns. For example, the word ‘people’ has a unique pattern in English, with the P and the E being repeated in that specific order. So in this basic substitution cipher, it would show up as ‘16-5-15-16-12-5’ or more likely, ‘1651516125.’ ” Charlie sketched out what she meant:

  P

  E

  O

  P

  L

  E

  16

  5

  15

  16

  12

  5

  “But the problem is,” she continued, “I have no idea what language Einstein would have set up this cipher to translate into. The guy spoke German, French, and English fluently—and for all I know, he spoke Portuguese and Esperanto, too. Then again, maybe this doesn’t translate into words at all. If Pandora is a formula, then maybe these numbers just translate into more numbers.”

  Leaning over the back seat, Dante shared a look of frustration with Milana as they both realized that the clue was far more complicated than they’d hoped—and that perhaps Charlie was right that it might take months or more to solve.

  Rats turned the SUV off a road choked with cars and tourists onto a surprisingly quiet residential street in the Jewish Quarter. The bustle and noise of the city seemed to disappear, as though they were suddenly a hundred miles away from everything, instead of mere yards. However, Rats still had to drive slowly, as the street had been built hundreds of years before anyone had even imagined a car. It was so narrow at points that the SUV could barely fit between the buildings.

  Dante said, “Let’s start with the assumption that this clue translates into a language. Do you see any patterns at all?”

  “Not really,” Charlie replied. “Only four numbers appear more than once: Five and fifteen appear twice, while ten and sixteen appear three times. Then there are two Ms and three Xs. But that’s a very low frequency of repetition. For example, in English words, the letter E is so common it appears about once every twelve letters. And I think it has a similar frequency in German. Now, I don’t know about other languages, but I’d have to assume that . . .” Charlie trailed off suddenly, struck by something.

  “What is it?” Milana asked.

  “I’m an idiot,” Charlie said. “I’ve been looking at the numbers instead of the variables. There are only four variables in this clue. Do you see what they stand for?”

  Milana shook her head. “They could stand for lots of different things. M could mean meters, milliliters, miles . . .”

  “Or mass,” Dante added. “Like in E equals MC squared.”

  “And C could be centimeters, centiliters, or the speed of light,” Milana said. “Meanwhile, X generally represents an unknown variable, while I stands for imaginary numbers. That’s a strange collection of variables to find in one equation. . . .”

  “Exactly,” Charlie said. “But if you pull them out of the equation, you get something completely different.” She pointed to the variables in order.
“MCMXXXI.”

  Milana’s eyes widened in surprise. “Roman numerals.”

  “1931,” said Charlie.

  Dante swung around in the front seat, looking impressed. “You think Einstein means the year?”

  “I suppose,” Charlie said. “I’m not sure what else he could mean.”

  Milana said, “In 1931, Einstein was still living in Germany, teaching at the University of Berlin.”

  “Maybe that’s the year he found Pandora,” Dante suggested.

  “Maybe,” Charlie agreed. “But if so, it still doesn’t give us much insight into what the rest of the code means.”

  Rats suddenly stopped the SUV.

  Charlie pulled her attention from the code and looked out the window.

  The quiet, twisting street they were in had come to an end—sort of. Ahead, it narrowed too much for the SUV to fit through, becoming a pedestrian route.

  They were in a residential area, surrounded by homes. Each was hundreds of years old, but had been updated for the modern world. All were three stories tall, built of the same Jerusalem stone, and were connected, wall-to-wall, creating a sprawling, misshapen block. From the outside, it was impossible to tell where one house started and the next stopped. Ahead, the room of one home even formed a bridge over the narrow street.

  Rats had parked in front of a house with a garage, which Charlie realized was highly unusual in the Old City. Right next to the garage door was a heavily secured entry door with a coded-entry keypad and a camera mounted above it. This struck Charlie as a blatantly obvious security system—the kind of thing that screamed “secret CIA headquarters”—until she noticed that every other residence around her had the same thing. Apparently, people in this section of the Jewish Quarter were very concerned about safety.

  “Is this a safe house?” Charlie asked.

  “Brilliant deduction,” Rats said sarcastically, hopping out of the SUV.

  The moment his door was open, the sounds of the city filtered back to Charlie. Ahead, down the narrow section of the road, she could hear the chatter and bustle of what might have been a market street.

  Rats typed a code on the keypad by the front door, and the garage door rose. He hopped back into the SUV and drove inside.

  The inside of the garage confirmed to Charlie that this wasn’t a normal home. Normal homes would have had things stored in the garage, like bicycles and tools and old cans of paint. Especially in a crowded place like the Old City, where space was probably at a premium. This garage had none of that. There were only a few shelves of supplies in bulk: toilet paper, window cleaner, toner cartridges.

  Everyone piled out of the SUV as the garage door slid closed behind them, cutting out the sunlight. The only other exit was through a door into the safe house. Rats led the way through it, Milana following him.

  In the garage, Charlie turned to Dante and asked, “What’s the deal with you and Milana?”

  Dante’s steps faltered, ever so slightly. “There is no deal with me and Milana.”

  “You like her, though, don’t you?”

  Dante’s face remained stoic, but Charlie noticed the tips of his ears turn red from embarrassment. “My relationship with Agent Moon is purely professional.”

  “That’s a shame. She likes you too.”

  “She does?” Dante asked, unable to stop himself—and then immediately regretted it.

  Charlie grinned, pleased to have found a chink in her brother’s hard exterior. “I knew it! You like her!” She began to sing tauntingly. “Dante and Milana sitting in a tree! K-I-S-S-I-N-G . . .”

  “Quiet!” Dante hissed, and Charlie fell silent.

  They passed through the doorway from the garage into a small foyer. To their right was the door to the street. To their left, a staircase led up to a second security door, which Charlie figured protected the rest of the safe house.

  Rats and Milana were already at the top of the stairs, by the second door, waiting for them. Dante waved them on. “Head on in,” he said. “We’ll be up in a few.”

  Rats entered a code on the keypad and the upstairs door clicked open. Then he and Milana passed through it—although Milana gave them one last look before entering.

  “That’s what I’m talking about,” Charlie said. “That little glance she gave you? Did you see how she was looking at you?”

  “I didn’t see anything,” Dante said.

  “You didn’t? Jeez, you might know a whole lot about terrorist cells, but you don’t know much about women. That was a full-on ‘I wish Dante would say to heck with the regulations and just kiss me’ look.”

  “You’re full of crap,” Dante said, although he couldn’t hide the fact that he was really hoping that Charlie spoke the truth.

  “I am not,” Charlie said. “This is how she was looking at you just now.”

  Dante turned to face her.

  Charlie hammed it up, fluttering her eyelashes and puckering her lips. “Oh, Dante,” she cooed. “You’re soooo dreamy.”

  “Can it, you little jerk,” Dante said, although he was smiling, pleased by the thought of Milana Moon liking him, dropping his guard around Charlie.

  Which was exactly what Charlie had been waiting for. The time had come to put her own plan to protect Pandora into action, but she needed to work fast.

  She quickly drove her knee into her brother’s crotch.

  Then, as Dante doubled over in pain, she bolted through the security door into the street and ran as fast as she could.

  TWENTY-TWO

  While it might have seemed reckless for a twelve-year-old girl to flee from a safe house and head out alone into a foreign city, Charlie had a plan to survive. She had been working it out from the moment she had first arrived in Jerusalem.

  The sun was blinding as she emerged from the dark stairwell of the safe house, and her body was still hurting from her fight with Marko, but she didn’t stop moving. Her ruse had bought her only a few seconds. She raced into the narrower section of the street, toward the noise and bustle she had heard before. If she could make it to where there were people, she could blend into the crowd.

  However, there was something Charlie needed to do even before she had ensured her escape.

  She crammed Einstein’s clue into her mouth and chewed.

  She rounded a corner and found herself in a crowded bazaar. The whole thing was underground, in an arched passageway that appeared to be thousands of years old. Alcoves in the ancient walls were filled with shops. Unlike the other markets Charlie had seen so far, this one wasn’t for tourists, selling souvenirs; instead, it was for the residents of the Old City, selling the basics of daily life. Tailors slaved over ancient sewing machines; grocers hawked fruit and vegetables; spice merchants displayed tables full of their wares; butchers hacked apart sheep carcasses with cleavers. As Charlie had hoped, the market was filled with people, most with loaded shopping bags slung over their shoulders. She ducked into the crowd, hoping to quickly disappear.

  Something slammed into her from behind.

  It was Dante. Either her knee to his crotch hadn’t hurt him as much as she’d hoped—or the man had an impressive tolerance for pain. Charlie was thrown several feet by their combined momentum and crashed into a kiosk selling fresh fruit. Dante landed on top of her, crushing the wind from her lungs, while a table full of figs upended on top of them.

  Charlie struggled under her brother, but as she had learned when fighting Marko, she was no match against someone who was actually trained to fight. She had caught Dante off guard once; he wasn’t going to let it happen again. He shoved her down on the hard stone, then jabbed her in a pressure point at the back of her neck that she’d never even known she had. Pain shot through Charlie’s body. She screamed, unable to control it, and Dante snatched Einstein’s clue right back out of her mouth.

  “You stupid little punk,” Dante snarled, and then wrenched Charlie’s arm behind her.

  “Ow!” Charlie yelled. “You’re hurting me!”

  �
��That’s the point. And I can make it a lot worse.” Dante roughly yanked Charlie to her feet.

  The kiosk’s owner was shouting at them in Hebrew, angry about the destruction of his property.

  “Help me,” Charlie said to him in Hebrew. “This man is trying to abduct me!”

  “Don’t listen to her,” Dante said, surprising Charlie by speaking in Hebrew himself. He flashed his badge with his free hand and said, “I’m CIA, working with the Mossad. This girl is connected to an anti-Semitic terrorist cell.”

  The people surrounding them backed off, now glaring at Charlie hatefully. A few even spit at her. Only the kiosk’s owner held his ground, still shouting at them until Dante fished some crumpled bills from his pocket and handed them over. “This ought to cover the damage.”

  That quieted the vendor. He immediately began cleaning up the mess Charlie and Dante had made.

  “You’re not the only one in the family who can speak multiple languages,” Dante told his sister, keeping her arm twisted behind her back. He checked Einstein’s code, confirming that Charlie hadn’t destroyed it, then shoved it in his pocket and clamped his hand on her neck.

  In that position, Charlie had no choice but to march back toward the safe house.

  “Here I was, thinking that I’d been wrong about you all these years,” Dante muttered. “Thinking that you weren’t just out for yourself. That you actually had some decency in you. And then, even though you know what’s on the line here, you still put your own freedom ahead of the safety of millions of people.”

  “I was trying to protect those people,” Charlie shot back. “You’re the one who’s putting them in danger.”

  “Really? You didn’t just try to escape with the clue to Pandora’s location?”

  “No. I tried to destroy it. If the point of this mission is simply to keep Pandora from ending up in the hands of our enemies, then solving the clue isn’t necessary. All we really have to do is get rid of it.”

  A flicker of worry flashed in Dante’s eyes.

  It was a small reaction, but it instantly confirmed Charlie’s worst fears. “However,” she said, “the point of this mission isn’t simply to keep Pandora away from our enemies, is it? It’s to get Pandora for ourselves.”