The Eureka Key

  “Find something to use as a lever!” Mr. Flintlock’s voice came faintly from behind them. “Hurry up!”

  “An abandoned gold mine, I bet,” Theo answered, moving farther into the tunnel.

  “That’s a good guess,” Martina agreed. “Death Valley was part of the Gold Rush, back in the nineteenth century.”

  “And you look like some kind of old-timey prospector with that thing on your head,” Sam told her as they both followed Theo. “If you hadn’t had such good aim with that flashlight, I’d tell you how ridiculous it looks.”

  “Is that actually a Sam Solomon attempt at saying thank you?”

  “Come on, you two!” Theo’s voice was impatient.

  “You think they can really pry that stone door open with their fingernails?” Sam asked, catching up with him. “Those guys looked tough, but not that tough.”

  “That helicopter is almost definitely full of supplies,” Theo answered grimly. “Plastic explosives. Detonators. Everything they need. At least that’s what I would bring.”

  Sam blinked. “Of course that’s what you would bring, Theo. Because you’re just a normal kid who won a contest, right?”

  “Sam, he’s right,” Martina said. “We’d better—”

  But Sam had stopped in his tracks. “No,” he said sharply. “No! I am not moving from this spot until he tells me what is really going on here.”

  Theo turned around, frowning, covered in dust and grit from his dark hair to his boots, his head brushing the top of the tunnel. Massive. Like a giant. Or an action hero. Not like any kid Sam knew, that’s for sure.

  What ordinary kid knew all about detonators and plastic explosives? What ordinary kid wasn’t even surprised when a tourist pulled out a gun, and a helicopter full of bad guys showed up?

  “What do you mean?” Martina asked. “Why would Theo know any more than we do about these guys?”

  “Are you kidding me?” Sam exclaimed. “Look at him! Look at his face! He knows something. I bet Evangeline does too. This trip has been a disaster since the moment we stepped on that plane, and Theo is going to tell us why.”

  “Sam, look—it has been suspiciously insane, but maybe this isn’t the best time to talk,” Martina said, casting an anxious glance over her shoulder.

  “Why did that goon with the Hawaiian shirt act like he knew who we were? What was that crazy sundial puzzle doing in the middle of the desert?” Sam didn’t look away from Theo. “Who put it there and made sure it would vaporize anybody who got the answer wrong? Why are we here, Theo?”

  Theo studied Sam’s face for a few seconds. Sam expected the kid to tell him off, to say he was crazy, maybe even to confess that they really were all on some kind of twisted hidden-camera reality show. But what ended up coming out of Theo’s mouth was something completely unexpected.

  “What do you know about Benjamin Franklin?”

  Sam wanted to scream. “Benjamin Franklin?” he spluttered. “Really? Listen, I’m not interested in pop quizzes while I’m inside a pitch-black abandoned gold mine being chased by men with guns! I told you, I want the truth!” Sam stomped his foot on the stone floor for effect.

  A moment later, something shifted under his boot, and the ominous sound of stone grinding on stone filled his ears once more.

  “Uh-oh,” Sam said.

  “What’s happening?” Martina looked wildly around, sending the light from her head lamp swinging. Just as it settled on what looked like a stone button depressed into the rock floor, Sam felt the ground give way beneath his feet.

  And then they fell.

  CHAPTER EIGHT

  Sam felt a sickening lurch as he dropped into a deep shaft, which must have been hidden under the cave. He flailed, trying to grab on to something, but only managed to crash into a rock wall on one side and Martina on the other. It was no use. He braced for the impact.

  But instead of the cold, hard ground, he hit—

  Water! Cold water fountained up around him with a splash that rivaled his best cannonball at the neighborhood pool. He had about half a second to be relieved that he wasn’t dead before the water closed over his head.

  He was sinking. He was drowning!

  Sam kicked and struggled, his heavy boots dragging at his legs, his backpack weighing him down like an anchor. He forced his eyes open, but blackness was all around him, as suffocating as the water. With no sense of direction, Sam had the horrifying realization that even if he could swim, he’d have no idea which way to go.

  And then, somewhere nearby, a white light glimmered like a ghost in the darkness.

  His chest aching fiercely, Sam shoved the straps of his backpack off his shoulders and struck out for the wavering beam of light that sliced through the water. Martina’s head lamp! A few seconds later, he broke through the surface, his breath coming in ragged gasps.

  “That head lamp . . . that thing’s . . . waterproof?” Sam choked out, kicking hard to keep himself afloat.

  “That’s the first thing you’re going to say to me?” Martina spluttered. “How about, ‘Gee, Marty, nice to see you’re not dead!’” Theo was bobbing beside her, looking a little worse for wear. His dark-brown skin had suddenly gone a pale shade of gray.

  “Fine, fine,” Sam said, grabbing at a lump of rock sticking out from the wall. “But what the heck is this place? I thought Death Valley was supposed to be dry!”

  Martina seized the edge of the wall as well, sucking in several breaths.

  “An underground water source, I guess,” she panted. “Must have filled up one of the old mine shafts . . . Sam—are you laughing?”

  Sam suddenly found himself giggling like a maniac. “An oasis!” he choked out. “Just like that inscription next to the sundial said! Too bad the poem hadn’t mentioned we were going to drown in it!”

  It took a special talent to drown in a desert. He hoped they’d mention it in his obituary.

  “Sam!” Martina snapped, and then coughed. She lost her grip and floundered for a moment, then managed to wedge her fingers into a crack. “Get it together!”

  “Right. Sorry.” Sam gasped, swallowing his laughter along with a mouthful of water that tasted like mud. “It was just—kind of funny. So. Okay.” He shook his head, got in a steadying breath, and realized that Martina looked different—and it wasn’t just that she was soaking wet. “Hey, Marty, where are your glasses?”

  “Where do you think?” Martina shook her clinging hair out of her face. “At the bottom of the mine shaft, probably.”

  “Can you see without them?” Sam asked.

  “I can see you wasting time asking me dumb questions! Forget the glasses for now. We need to find a way out of here!” The light from Martina’s head lamp swung around, revealing slick, wet walls high over their heads. No ladder. No rope. Nothing.

  “There’s no way we can climb the walls,” Sam said. “Way too slippery.”

  “Well, we can’t stay here,” Martina said.

  “No kidding,” Sam agreed. “And it’s not like anybody’s going to show up to rescue us.”

  “The only people likely to show up . . . are Flintlock and his men,” Theo said, a little breathlessly.

  “Can’t go up, can’t stay here,” Sam went on. “So we have to go . . .”

  “Down?” Martina gazed at the cold, black water all around them.

  “Down,” Theo said. He took a deep breath and dived.

  But he didn’t get far before bubbles exploded in a flurry across the water’s surface. Theo’s head reappeared. His face was twisted with pain.

  “Theo!” Martina, who was nearer, grabbed for him.

  “No, don’t!” Theo pulled away. “My shoulder—don’t touch it.”

  “Give me your other hand,” Martina insisted. Theo let her take hold of his left arm, wincing.

  “What’s wrong?” Sam demanded.

  “I think my shoulder’s dislocated,” Theo groaned. “I tried to break my fall on the way down, but we were dropping too fast. Jerked it out of the
joint, I guess . . .”

  “So you can’t swim?” Sam asked.

  Theo’s face crumpled. For the first time since they’d met, the big guy actually looked like what he was—a kid. “No,” Theo said, his voice heavy with shame. “I guess I can’t.”

  Despite how angry Sam was at Theo for keeping secrets from them, he felt sorry for the guy. “Hey, man. Don’t worry—we’ll get out of here. Marty, give me that lamp thing.” Sam held out his hand for Martina’s head lamp.

  “It should be me going down there,” Theo said.

  Sam chuckled humorlessly. “Don’t worry,” he replied. “Somehow I have the feeling you’ll have another chance before this day is done.”

  Theo nodded. “Be careful,” he said, his voice tight with pain.

  “Take a couple of deep breaths before you dive.” Martina watched as Sam struggled to get the head lamp’s strap around his head without letting go of his grip on the wall. “It’ll help raise the oxygen levels in your blood.”

  Sam did as she suggested, then sucked in a huge breath and dived.

  Sam’s time in the two-hundred-meter relay used to be pretty good. But tearing down the lanes at a nice, clean, brightly lit pool hadn’t really prepared him for swimming down into utter blackness in a T-shirt and jeans.

  The head lamp’s ray pierced the murk like a knife as he swam down, but there was nothing to see but water. He kicked hard, even though his feet in their heavy boots felt clumsy. He would have killed for a pair of flippers. He swam deeper and deeper, but there seemed to be no end to this mine shaft, or to the darkness of the abyss.

  Sam was beginning to get disoriented, so he was about to turn back before he lost his bearings when the torchlight bounced off something that wasn’t water. Polished stone, maybe? No, it had a metallic shine to it. It was metal—brass. A rectangular brass door had been set into one side of the mine shaft’s wall.

  Sam stopped swimming, letting the weight of his clothes and boots pull him gently down toward the floor. His chest was starting to ache again. He needed to save enough air to make it back to the surface, so he could only afford to spend a few seconds to get a sense of what was he was dealing with before he had to head back up.

  First, the door. A door was good—a door meant a way out. But Sam couldn’t see a knob, handle, keyhole—anything. No way to get it open.

  His eyes took in what was on either side of the door. On the right, there was a hole as wide as Sam’s body, covered by an iron grate. On the left, he saw a three-by-three-foot square etched into the stone. More than a square—a grid. Every little square inside the big one was filled with a number. Every square but three. Those three were blank. And each of the blank squares had a hole in its center.

  He knew instinctively that it was another puzzle, like the sundial on top of the mountain. But who in the world was going around creating deadly puzzles in an old gold mine in the middle of a national park? And why?

  Maybe it’s Benjamin Franklin, Sam thought with a semihysterical chuckle.

  Sam turned the beam of his head lamp to the floor of the tunnel. His backpack was in one corner, and Martina’s was nearby. Sam had a moment of grief for his comic books before he was distracted by the sight of a dozen little stone tiles littered all over the floor. Each had a different number and a metal prong sticking out of its back. They looked just the right size to fit into the empty squares on the grid.

  Bingo.

  The pressure in Sam’s chest was tightening, as if someone was turning a screw in his ribs. He was out of time. Planting his feet against the floor, Sam pushed off as hard as he could and shot upward through the water. His vision had just started to cloud from lack of oxygen when he broke through the surface, heaving in huge breaths.

  “Well? Did you find anything?” Martina looked over eagerly as Sam grabbed hold of his friendly hunk of rock once more. But she had to wait until he could breathe again for her answer.

  “Door,” Sam gasped out finally. “But no way . . . to open it. And numbers. A grid on the wall. Like a mega-sudoku kind of thing. With three numbers missing.”

  “Sudoku?”

  Sam nodded. “Yeah, but a lot bigger. And there weren’t any repeating numbers like there are in sudoku. They looked random—double digits, single digits—like nothing I’ve ever seen before. But there’s got to be a pattern.”

  Martina hesitated a moment, a thoughtful look coming over her face. She turned to Theo, hanging onto her shoulder, his face looking even grayer than before.

  “You mentioned Benjamin Franklin,” she said. “Why?”

  “Ben Franklin?” Sam exclaimed. “What is with you two? The Founding Fathers are not going to help us now.”

  Theo pursed his lips, as if there were a secret resting on his tongue and he wasn’t ready to let it out.

  “Maybe they are,” Martina insisted, giving up on Theo for the moment. “Listen, Franklin developed a puzzle. It was a lot like sudoku. He called it a Magic Square of Squares.”

  Despite himself, Sam was intrigued. “Explain.”

  “Well, every row and every column in the grid add up to the same number. And there are ‘bent-rows’ too—diagonals that look like V’s, on each side of the grid—they also add up to the same number.”

  “Okay,” Sam said slowly. “Let’s say you’re right. I still don’t understand what the guy on the hundred-dollar bill has to do with some death trap in the middle of—”

  Sam’s words were interrupted by a huge boom that reverberated through the cavern, sending the water around them sloshing and bits of gravel and rock raining down on their heads.

  Sam swung the head lamp’s light up the mine shaft, but there was nothing to see but dust motes floating through the air. But he didn’t need to see anything to guess what had happened.

  “Plastic explosives?” he asked Theo, who nodded. The kid’s jaw was tight and he was taking in slow, careful breaths, trying to keep his body still in the water.

  “Sam!” Martina said, an edge to her voice. “If it’s really one of Franklin’s magic squares, you need to figure out if the sum of those rows and columns is the same number. It’s the only way to solve it.”

  “Okay,” Sam replied. “I’ll be right back—don’t leave without me.”

  Martina gave him a halfhearted glare. “Funny.”

  Sam took another breath and dived.

  He could replace the missing numbers. Solve the puzzle. He’d never let a puzzle beat him yet. He could do this.

  Right?

  Down, down, down—as fast as he could go. Soon the puzzle was in the glow of the head lamp once again.

  Okay. It was just math. He could do math with his hands tied behind his back. Or, in this case, under a hundred tons of water. In the dark. Sure! After this trip, algebra tests would be like a walk in the park!

  He cleared his mind, pushing away the fear so that he could focus on the puzzle in front of him. He quickly added up several rows and columns—twice, just to be sure. Martina was right. They all added up to the same number: two hundred and sixty.

  So that number at the bottom of the far-right column should be a seventeen. Sam scrabbled in the tiles beneath him. Seventeen, seventeen . . . there! He shoved the tile into place, forcing the metal prong into its hole. He felt something vibrate inside the stone, like tumblers in a giant lock falling into place.

  His lungs were starting to burn. The urge to inhale was fierce, but he fought it. The second missing number, the one closest to the top . . . it had to be six. He’d seen that one as he was looking for the seventeen! He scrabbled in the dirt and had inserted it in five seconds flat.

  He was so close to solving it—but his lungs were screaming for air. He had no choice—he had to go back.

  When he finally surfaced, he could only cling to the rock wall for a minute or two, choking down breaths, unable to speak.

  One more. That was all. He looked up, shaking water out of his eyes. “Listen, guys. I’ve almost got it. I . . .”

 
But it didn’t look like Theo could hear him. Eyes half shut, he didn’t even seem to notice that Sam was there. His head had fallen limply against Martina’s shoulder. She hung on to him with one hand, struggling desperately to keep his face above water.

  “He passed out a few seconds after you went down,” she said, her voice shaking. “I don’t know how much longer I can hold him. If we don’t get out of here soon . . .” She stopped, as if she didn’t like how the sentence might end.

  Above, a shout—“We’re in!”—echoed off the stone walls. Footsteps on stone. Flintlock and his men had finally broken through the door.

  “Better . . . leave me,” Theo mumbled without opening his eyes.

  “Don’t be an idiot,” Sam gasped, and dived.

  He wanted to tell them that everything was going to be okay—he had only one number left to go—but there wasn’t time. Better to save his breath for swimming.

  Sam’s whole body was angry with him. He was hungry and so tired . . . but he kept pushing his arms through that water, forcing himself deeper and deeper, until he reached the bottom.

  Okay—it’s go time.

  He squinted at the bottom row, where the last number was missing. Even with a brain starved for oxygen, Sam could figure it out. One! The last missing number was a one!

  Sam pawed through the stone tiles. Over and over he spotted a one—but it was always next to some other number: 41. 19. 12. 81.

  The last tile he needed to solve the puzzle was nowhere to be found.

  CHAPTER NINE

  Had Sam been wrong? Had he missed something? Made a mistake in his math? Maybe that was why there was no tile with a one on it—because it wasn’t the right answer.

  Sam had told Martina that everybody got things wrong sometimes.

  But not him.

  Not now.

  He couldn’t afford to make a mistake, because with Theo passed out up there, Martina trying to hold on, and scary guys hurrying their way, getting it wrong wasn’t just a bad score on a math test. He thought about adding the lines again, but he knew he didn’t have the precious seconds.