Kylie ran towards her fallen dragonfly and knelt beside it. One of its four wings had snapped nearly in half. She rummaged through a toolbox until she found a small tube of accelerseal, bit off the cap and squeezed a generous amount onto the wing's fracture, holding the two pieces together. Above her Mark's velociropter circled and swooped, its four propellers buzzing, its gratuitous crown of metal claws gleaming. He was standing opposite Kylie inside a large wire cage in Montarbor High School's gymnasium. His classmates cheered from bleachers to his left. She could hear her team booing back.

Once the wing had healed, Kylie flipped her dragonfly right side up and stood beside it. She extended her right hand, on which she wore a long and rather elaborate silver glove sewn through with wires, accelerometers and pressure sensors. As she lifted her hand, the dragonfly's motors stirred; its wings began to whir; it rose slowly but determinedly into the air. Mark turned his own gloved palm toward his chest, fanned three fingers and jerked his whole hand rightward. A ring of blades emerged from the rim of his velociropter, which started to spin maniacally. Kylie made a fist and turned it upside down. Her dragonfly dove almost to the ground, flew all the way across the playing field and began a quick ascent, somersaulting backward to face the velociropter once again.

By jutting her thumb and pinky outward, Kylie extended a long thin needle from the dragonfly's head. Mark laughed. "Well that's new. You going to knit my drone to death?"

"Maybe I'll just sew your lips shut," Kylie shouted back. She pumped her fist forward. Mark did the same. The drones sped toward one another and collided, each ricocheting a considerable distance. The dragonfly's needle had snapped as easily as an old rabbit ear TV antenna. "Impressive," Mark said. Only then did he notice that his drone had lost a piece of its crown.

The referee called time out so a boy on the sidelines could clear the debris. When the match was back on, Kylie pointed her fingers skyward as though greeting someone and quickly swiveled her wrist. Her dragonfly rose to the very top of the cage with incredible speed and attempted to initiate a dive bomb, only to stall and fall, twirling like a maple seed. Kylie's eyes widened. She made the same set of gestures over and over, but her drone did not respond.

"Today is just not your day," Mark said, positioning his velociropter to ram the dragonfly at the right moment. Had he looked more carefully at Kylie's face, he might have seen her repressing a smile.

She waited—one, two—and sliced her hand through the air like a scimitar. The dragonfly spun itself into a blur, halting its descent, and did a kind of bicycle kick. A small torpedo-shaped projectile flew from its tail and struck Mark's velociropter, which convulsed mid-air in a shower of sparks and fell to the ground. Mark and the referee huddled over the motionless machine. After a few seconds, the referee stood up, pointed to Kylie and blew his whistle. Everyone on the bleachers to her left cheered as "Drone Duels Winner: Mosston High School" flashed on the scoreboard.

Using his shirt for protection, Mark pulled the culprit out of his velociropter. "What is this?" he asked as Kylie walked over.

"Think of it as a wireless stun gun," she said. She took the projectile from his hand. "It delivers an intense electric shock upon impact. There's a really tiny high voltage battery back here. And it's got these metal and magnetic teeth to help it stick. I call it a petrifly."

"Please tell me this is the only one you made," Mark said.

Kylie smiled.

Mark turned to the referee. "Look at this thing," he said, waving at the petrifly in Kylie's hand. "We've never used projectiles before. This has got to be against the rules, right?"

The referee shook his head. "Actually a kid at Clearview has a drone that shoots a net. Pretty effective at tangling propellers. Besides there's nothing in the book against this. She OKed it with us beforehand."

Grimacing, Mark began to exit the cage.

"Hey, come on," Kylie started, but Mark kept walking.

Jacob, one of Kylie's teammates, put a hand on her shoulder. "Let him go," he said. "He's been an especially sore loser lately."

***

Later that night, drone duelers from various Silicon Valley high schools gathered at Jacob's house for a party. "Remember," Jacob said, walking into the living room with two large blue buckets, "all cans and bottles go in the designated receptacles. I got to haul all this stuff out tomorrow morning before my parents get back."

A boy approached Kylie, who was talking with her friend Ruth. "Hi, I'm Nathan," he said.

"Hi," Kylie said. "You look familiar."

"I'm Ben's younger brother."

"You mean Ben Flegerston? As in Mark's best friend?"

Nathan nodded.

"I didn't know he had any siblings."

"Yeah, just me. I'm a freshman at Montarbor now."

"Cool." They both looked at their drinks.

"Anyways, I just wanted to say that you were awesome today."

"Well, thanks," Kylie said. "You hoping to join the Montarbor team?"

"Yeah," Nathan said. "Who knows, maybe we'll get to play against each other next semester."

"Maybe."

"So, if it's okay, can I ask what you were trying to do with that needle? I mean, was it supposed to—"

"Fraternizing with the enemy already, Nate?" Ben said as he and Mark sidled up to the group.

Nathan stayed quiet.

"Maybe you should remember whose house you're in," Ruth said.

"That's circumstantial," Mark said. "It would be a waste to pass up such nice digs when they are so conveniently vacated."

"Guys," a voice called from the stairway, "you got to see this." Emile emerged from the hallway holding his laptop. "Jake, can we connect this to the TV? Seriously, everyone should watch."

It was a promotional YouTube video by Xchange.com, a major online retailer. A man wearing thick-rimmed glasses and a plain blue polo sat in front of an uncomfortably white background. A caption identified him as Henry Furtumund, Xchange's CEO.

"Throughout history we have relied on things that can fly to deliver our messages and packages," Furtumund began. "Falcons. Pigeons. Planes." As he spoke each noun, it appeared behind him in giant font. "Now it's time for something new. Time to launch a new era of delivery service and open the skies to a whole new kind of postmaster: the drone."

What looked live five flying metal octopuses whooshed onscreen and circled his head. Each had a bulbous glass dome surrounded by eight propeller-tipped arms, beneath which dangled four spidery legs.

"Holy…" said Mark.

"This is awesome!" Ben yelled.

"Three years ago," the CEO continued, "many people laughed at our proposal to deliver your purchases by drone. Even we were conservative in our predictions. But our engineers have come up with some game-changing, revolutionary, breakthrough technologies that will totally transform home delivery forever." His choice adjectives ballooned on the white background.

"We have made these drones from a brand new kind of porous polycarbonate modeled on birds' wings. It's durable and incredibly light. Our drones draw power from two different ultra-compact batteries, one of which is solar powered, giving them an amazing 36 hours of flight time without needing to recharge. And they can carry up to seven pounds, which means they can transport more than 80 percent of the items we sell. Xchange's drones are completely autonomous, but we can override their systems in an instant if we need to."

Kylie looked like she had just smelled skunk. "What's wrong?" Ruth whispered. Kylie just shrugged.

"Although the Federal Aviation Administration is still working on a final draft of its rules and regulations for commercial unmanned aerial vehicles, they have granted us permission to begin using our drones in select locations across the country," Furtumund continued. "Our delivery drones officially start work in 30 days, on January 15th, but we're offering a special Christmas Day delivery service for the Silicon Valley. On December 25th we will be making drone-assisted early morning drop-offs at houses within a 15-mile radius of our headquarters. This option is available for anything purchased between now and December 24th."

As the camera panned right, the five drones whizzed off-screen, only to return momentarily with three friends. All eight drones now sported tiny antlers and were tethered together by a jingle bell harness. A giant red LED glowed on the lead drone. The last in line towed a banner that read "HAPPY HOLIDAYS FROM XCHANGE!"

"This is amazing," Mark said. "I actually kind of forgot that Xchange was planning this."

"Something doesn't make sense though," Kylie said. "Why would the FAA give them the OK before ironing everything out?"

"Who cares!" Ben said. "This is going to be so sweet. I'm going to order so much stuff."

"It looks like the FAA's restrictions are a little tighter than Furtumund let on," Ruth said, scrolling through an article on her phone. "After this holiday gimmick, they're only letting Xchange fly the drones for a three month trial period."

"Hmm," Kylie said. "That still seems odd. It's almost like they've been forced or persuaded to—"

"Kylie, Kylie, Kylie," Mark said, putting his arm around her shoulders. "You used to be fun. What happened?"

Kylie eeled out of his grip. She was about to say something less than kind, but it occurred to her that Mark might be trying to smooth things over—however clumsily—so she tempered herself. "I'll admit, the technologies he described are pretty cool. I guess it just took me by surprise."

"Me too," Mark said. "But I like surprises."

"Yeah," Ruth said, "like the way Kylie surprised you in the cage today?"

Everyone laughed. "Fair enough," Mark said.

***

Dressed in jeans and black hoodies, Nathan and Ben walked briskly along the sidewalk, approaching Mosston High. Mark was a few feet ahead of them. Nathan glanced at his wristwatch. 3:36 AM. "Ben, we shouldn't be doing this," Nathan said.

Ben turned to face his brother. "You want to be part of the team or not?" Nathan nodded. "Here, give me the slacer," Ben said. "We're almost there." Nate gave his brother what looked like the handle of a large switchblade. "Nice," Ben said. "How did you make this anyways?"

"I've been amplifying laser pointers since I was in middle school. Taking it to the next level was not that hard."

"And it can cut through metal?"

"Technically it will only have enough juice to weaken the metal. But then we can break it with something else. That's why I brought all this stuff." Nathan lifted his hoodie to reveal a toolbelt festooned with gadgets.

Catching up with Mark, the brothers walked through the parking lot—which was empty save for one green Honda—past the tennis courts to the locker rooms. "Are you sure they would be here?" Nate asked. "Isn't this for, like, sports equipment?"

"Mosston doesn't have separate facilities for engineering and robotics like we do," Mark said. "They store their stuff in the gym teacher's office. I learned all about it a while back from you-know-who."

Meanwhile, six miles away, you-know-who and Ruth were talking in Ruth's bedroom.

"Did you see that New York Times article about Convey's new delivery service?" Ruth asked.

"No," Kylie said. "Don't tell me…"

"Yep. Drones."

"But Xchange just announced their Christmas day extravawhatever three days ago!"

"I know. Convey's vice president said they were planning to start in a few months but they changed their minds for some bogus reason yadda yadda yadda. Here, you can read it yourself," Ruth said, "I saved the link." She tossed her phone across the bed to Kylie.

In an impromptu press conference this morning, Silicon Valley-based Convey, a major courier service, revealed that it will use a small army of drones to deliver packages to local customers on Christmas Day. Many tech experts say that, in retrospect, they anticipated this shocking announcement. Although the special offer is almost identical to one recently made by Xchange.com, Convey's vice president Samantha Argentum is adamant that her company's decision is not mere copycatting.

"We've been working on our skycap drones for years," Argentum said. "Like Xchange, we have received permission from the FAA to move forward with test runs. We intended to start this spring, but we've been, well, you could say we've been flooded with holiday spirit. We realized that Xchange or any one company on its own would be unlikely to meet the demand for Christmas Day deliveries. The people need options. This is about getting as many presents to as many people as possible. It's bigger than any single corporation."

Embedded in the article was an illustration of a skycap drone. It was a handsome machine with an impressive wingspan and a streamlined body that called to mind a manta ray—especially with its wings curved upwards at their tips. The whole drone was impeccably white except for the word Convey emblazoned in black on its flanks. A dark blue box fit into the drone's back the way a ski boot snaps into a ski. When the skycap landed at someone's house, the diagram explained, it raised its nose, unhitched the package and let it slide down its body to the ground.

Back at Mosston High, Mark was using a tension wrench and bent paperclip to break into the gym teacher's office. "Almost got it. There!" He pulled the door wide open and flipped on the light. "That's got to be the cabinet," he said, pointing. It was enormous, taking up an entire wall all by itself. A bulky padlock secured its two doors.

Mark knelt in front of the cabinet. "Give me the slacer," he said, holding out his hand. Ben gave it to him. "So how do you work this thing?" Mark asked, looking directly into it.

"Careful!" Nathan said. "Maybe I should—"

"Oh, I got it," Mark said. "I guess there's only one button." He pressed it and pointed the slacer at the padlock, on which a faint green dot appeared. "Nothing is happening," Mark said.

"You can't see the beam itself," Nathan answered. "But it's there. Just keep it steady and it will eat through the metal." Seconds later Nathan slapped the slacer out of Mark's hand.

"Dude, what are you doing?"

"Sorry, but it just hit me: this is not going to work," Nathan said. "We didn't think this through. The plan is just to take one and get out of here, so no one notices anything, right? Well what are we going to do with the padlock? Just leave it all hacked up on the floor? Take it with us? That's a dead giveaway. We don't have a replacement."

Mark and Ben looked at each other.

"Hey, don't give me that look," Ben said, "you're the one who insisted on using the slacer. This whole thing was your idea."

"Well it's your brother's stupid invention!" Mark said.

"Don't take it out on him. It does what it's supposed to. He's right—we didn't plan this properly."

Mark shoved the slacer toward Nathan. "Here, you can have this back. But we're not leaving until we find a way to get into that cabinet without anyone knowing."

"Oh, right, what are we going to do? " Ben said. "Just ask the lock to pretty please open for us?"

As Mark and Ben argued, Nathan stared silently at the padlock. Then he spoke. "Guys, I think I have an idea. There's something I've been wanting to try."

Nathan pulled several gadgets from his toolbelt, including what looked like a silver matchbox, a funnel-like object and a collapsible phone booth-shaped container that sat on a small rectangular base covered with dials. He suspended the funnel from the top of the container, plugged the silver box into his phone's USB drive and connected the two with a thin white cord.

"Wait," Ben said, "Mom and Dad got you a portable 3D printer?"

"No. I saved up for it myself."

Nathan jostled the padlock to expose the keyhole. "Someone hold this perfectly still just like this," he said. Ben complied and Nathan used the attachment on his phone to scan the lock with ultrasound. "Now from this angle, please."

"You're going to print us a key?" Mark said.

"Yep."

"Okay. Wow." Mark couldn't help but smile. "Consider yourself initiated."

The three boys stooped by the container, watching the funnel twitch this way and that, tirelessly squeezing out a key one thin layer at a time. "Will it be strong enough?" Ben asked.

"Definitely," Nate said. "Even the early prototypes of this material were pretty durable. Now it's crazy strong."

Ten minutes later the printer had finished and the boys were staring at the inside of the cabinet. Mosston High's five drones sat in a row on a single shelf. "A part of me really wants to smash that dragonfly," Mark said, arms akimbo.

"That's not why we're here," Ben said as he started to look through boxes on the bottom shelf. "My guess is that they will probably—no way!" Ben heaved a large box out of the cabinet. It was stuffed with petriflies.

"This is incredible," Nathan said. "She must have made each one by hand. There's at least a hundred in here."

"She always was precocious," Mark mumbled.

Ben held one between his finger and thumb. "Well, we got what we wanted. Now let's put the rest back and get out of here pronto."

"No," Mark said. "We're taking them all."

"But you said you just needed one," Nathan protested. "That you were going to study it, improve upon it and then slip it back in the cabinet."

"I changed my mind," Mark said. "I had no idea she made this many. It's not fair for one person to keep all of this locked up."

***

Around 6AM on Christmas morning, Silicon Valley residents and local news teams began to gather behind crowd control barriers surrounding the headquarters of both Xchange.com and Convey, which were only a few blocks apart. At Jacob's party a bunch of drone duelers had agreed to meet on the civic center's rooftop parking lot, where they expected to get a good view of the flying porters in action. Kylie and Ruth locked their bikes together against a parking sign and took the elevator up to the top floor. Several of their Mosston teammates were already there, as well as half the Montarbor team and a handful of duelers from three other high schools.

Jacob waved to Ruth and Kylie, who joined him at the rooftop's edge. "They should be starting any minute now," Jacob said.

"I'm getting it all on tape," Ruth said, taking her camera out of its pouch. "Although I was hoping the singularity would be a little more exciting than this."

"Ha, this is definitely not the singularity," Kylie said. "I'm not sure what to make of it, but I still feel uneasy."

"It's just a publicity stunt, really," Jacob said. "Now that we're here, I'm glad we're here, but I seriously considered staying in bed this morning. They're going to fly around on autopilot, sticking to predetermined paths, and drop off their little three-pound packages—big whoop. I'd rather watch a drone duels match any day."

"I see one!" Emile shouted from the opposite side of the roof, pointing toward the public library. Everyone raced toward him, repeatedly tracing a line from his finger toward the horizon with their eyes. "I see it too!" Mark yelled. "There's another one over here!" Ben called.

Within seconds crisscrossing strings of drones checkered the skies. Xchange's robots looked like jellyfish from outer space that had descended for an aerial tour of suburbia. In contrast, Convey's sleek gliders were more menacing than uncanny, ripping through the air with frightening speed and precision.

Mark rushed over to the Mosston gang. "Ruth, you're getting all this right?" But she was fixated on her phone. "Oh my god," she said. "Look at this vine someone just posted." She played it for everyone. It showed an Xchange drone and one of Convey's skycaps bumping into each other mid-flight, wobbling a bit, then colliding again.

"Didn't they build proximity sensors into these things?" Ruth said.

"You would think so," Kylie said. "Just how many people signed up for this delivery service anyways? They probably had to cap it at some point, right?"

"I don't know," Ben said. "They let my parents order fifteen packages." Everyone stared at him. "Well they had a lot of last minute shopping to do!"

"Look out!" Emile shouted, shielding his face with his hands.

One of the white skycap drones came spinning like a boomerang into the middle of the rooftop, crashing so hard that it dislodged its cargo and shattered a wing. Ruth yelped and gasped her forehead where a piece of shrapnel had struck. Her fingers came away bloody.

"They're fighting!" Mark said.

To the friends' right an Xchange drone stopped in place, dropped altitude and careened towards a skycap glider, bludgeoning it against the side of a building. Above them two skycaps titled their wings beneath an octopoid drone and sent it tumbling. All across the Silicon Valley drones were either failing to properly deliver packages or had largely abandoned their primary task, intent instead on destroying one another. As Mrs. Krapowski tended to her award-winning garden of succulents, an entangled Xchange drone and skycap glider dove straight into her birdbath. Seven-year-old Alexander was waiting impatiently for his parents by the Christmas tree when a metal octopus shot out of the fireplace and flew erratically around the living room, slamming into the grand piano and knocking nutcrackers off the mantle place. Just across the street, a skycap tried to rendezvous with own reflection in a bay window. And after dropping off its parcel, an Xchange drone inadvertently latched onto a curious labradoodle puppy. Jenny Patterson watched in horror as the drone struggled to take off, lifting the dog no more than an inch off the ground. "Give me back Snickerdoodle!" she screamed, pulling her pet and punching the mistaken machine.

"We have to do something," Kylie said.

"What are we supposed to do?" Ben said, admitting silently to himself that he was probably enjoying the spectacle a little too much.

"We've got to take them out," Kylie answered. "Or at least as many as we can. People are getting hurt." She gestured at Ruth, who was scrolling frenetically through Twitter.

"Xchange's official stance is that the self-defense algorithms built into the drones are malfunctioning," Ruth said. "Convey claims it has no idea what is going on. And both companies say they are shutting the drones down as fast as they can, but that it will take at least four hours."

"I thought they could gain instantaneous control if they had to."

"Apparently that only works within a two mile radius of the headquarters. Otherwise they have to drive out to the wherever the drones are."

"Even if we were going to do something, we can't get our drones," Mark said. "We're not allowed to use them outside of matches and workshops. They're locked up. I think we should just let it play out. Let the police shoot them down or something."

Kylie was puzzled by Mark's reluctance. This was exactly the sort of situation she would expect him to relish—the chance to take action, to be a leader, to be a hero, even. He had become increasingly prideful over time—and he could be outright callous—but she had never known him to abandon his friends or turn his back on anyone when they truly needed him.

"We're in a unique position to help," Kylie said. "And if we have to break into the locker rooms, I think coach will understand. We can use my petriflies. I made 150 of them and I've been working on a rapid-fire launcher, too. Ruth, Jacob—are you up for helping?"

They both nodded. "Let's get to the school then," Kylie said.

Mark, Ben and Nate looked at each other. "Wait," Nathan said, holding Kylie by the shoulder. "You're not going to find them at the school."

"Nate, what are you doing?" Mark said.

"Shut up," said Ben, thrusting his hand in front of Mark's face. "This is more important than you."

"What do you mean, Nate?" Kylie asked.

"We stole them. Me, Ben and Mark."

"It was Mark's idea, but we all did it," Ben said.

"You took my petriflies?"

Nathan nodded.

"All of them?"

"Yes," Ben said. "But Mark's going to return them. Right, Mark?" He grabbed Mark by the collar. Jacob did the same.

Mark nodded. "You can have your stupid toys. But I'm not helping you any more than that."

Kylie searched the face of the boy she had once admired so much—the one who had introduced her to drone dueling in the first place. He was all ambition and no integrity. She felt a wave of remorse threaten to wash over her, but it was not powerful enough to dilute all the adrenaline in her veins. "Everyone," Kylie said, addressing the group at large, "if you want to help tame these flying catastrophes, get your drones and meet in 30 minutes at the big oak tree in Cooper park. These delivery bots think they know how to duel. Let's show them how it's really done!"

Duelers cheered and raced toward the elevator. "Here," Nathan said to Kylie, handing her a small plastic key. "That will get you into the cabinet in your coach's office."

"But how did you?"

"Ultrasound scanner and 3D printer."

Kylie grinned. "Can you get the printing stuff and meet me at Mosston?"

"Sure."

Half an hour later a dozen drone duelers had assembled in Cooper park with their drones and piloting gloves. Jacob and Ben stood on either side of the cardboard box full of petriflies. Kylie and Nathan were handing out identical pieces of plastic shaped like a single dimple like from an egg carton. "Everyone take 12 petriflies from the box," Kylie said. "These plastic things will clip onto your drones, like so," she continued, demonstrating. "You load a petrifly into one, get your drone in the air and flip it to fire the fly at your target. Obviously you want to use any guidance software if you have it. Other than that, it's up to you. Bring them down however you can."

The friends fanned out through the suburban streets, most on bicycles, a few on scooters and a couple driving cars with the windows rolled down. Having equipped her dragonfly with a rapid-fire launcher, Kylie paralyzed twelve delivery drones in rapid succession. Since they were so new to the technology, others had a little trouble at first, but soon got the hang of it. With their long wings, skycaps were easier targets, though the bulkier octopoid drones seemed more susceptible to the electric shock itself. Ruth came up with a clever way of crashing drones into each other by corralling them with a magnet dangling from her own drone, nicknamed the Dipolar Bear. Drake Fullerton of Clearview High managed to capture several pairs of sparring drones using nets. And, true to its name, Jacob's hammerhead nailed more than a few wayward drones with well-aimed swings.

By noon every drone had dropped to the ground, having been knocked out by a competitor, incapacitated by a drone dueler or deactivated by its parent company. Kylie and her fellow duelers surveyed the damage. Debris littered the streets, rooftops and trees.

"That was epic," Jacob said.

Kylie nodded and looked at her sneakers.

"It's over now," Ruth said. "I don't think we'll be seeing any more delivery drones for quite a while."

***

Mark biked up his driveway, a giant duffel bag strapped to his back. He dismounted, opened the garage door and lugged the duffel bag indoors. Once the door was closed again, he zipped the bag open. Two delivery drones were inside, a little scuffed but relatively intact. He turned the skycap drone on its side, pried open what seemed to be a small control panel and touched a screwdriver to the metal surface. A spark flew.