The Case of the Wilted Broccoli (8 page)

Suddenly there was a thud right next to him as a driver jumped off the loading dock and strode toward the cab.

He had to give the signal. Oh, snap. The driver was right there, between Linden and the cab, and would hear the bark. But Linden didn't have a choice, he had to warn Elon and Willow for them to have a chance to get out. He took a deep breath, and then barked as loud as he could: RUFF! RUFF! RUFF!
 

The driver turned and stared at him.
 

Linden froze.

"What are you--"

Linden didn't wait to hear what he was going to say. He scrabbled under the ledge until he got to the opening between the next two trucks over, and then ran away.

He cleared the front of the trucks, and then veered to the right, toward the entrance.

Elon and Willow were right in front of them! They all ran as fast as they could, their sneakers slapping the ground, the wind blowing in their hair.

Distantly they heard a few shouts behind them, but they kept running as fast as they could, up the driveway, then down the street. They didn't want to stop in the neighborhood to catch a bus where the truck drivers might seem them when they left Bannon. They kept running, ten, fifteen, twenty blocks, until they finally pulled up gasping and sweating near a bus stop. They hid between a clump of trees, their hands on their knees as they tried to regain their breath.

"Well?" Linden finally asked between gasps.

"It's not the driver," Willow answered, straightening up and putting one hand on her ribs. "The food came on rotten."

Elon nodded. "We could see the driver talking to another driver. He didn't even do the loading. A bunch of other guys came and went. And they brought some nasty stuff on."

Linden felt himself flush and grow angry. "So what was the point of getting up so early? Nothing. We learned nothing about who's doing it."

"We learned the driver didn't," Willow said. "That's part of the process of elimination. We have to keep tracking it back further. We need to see where the guys loading it are getting it from."

"How are we going to do that?" Linden said. "We almost got caught as it was. We can't go inside the warehouse."

"Yeah, well, I have an idea about that," Elon said. "A way to watch them so that we can't get caught, and we can see everything they do."

CHAPTER SEVENTEEN

O
N
S
ATURDAY
MORNING
their dad made chocolate chip pancakes, and when the kids finished breakfast, they holed up in the garage with the door closed for privacy.

"Tell us the plan again," Willow said.

"We use the drone," Elon explained. "We need to finish it up this weekend, get it all working perfectly by Sunday night, including the live camera feed. Then on Monday morning, we go back to Bannon Foods. Instead of going into their parking lot, we'll go to the place next door that's always been closed and set up there. Then we fly the drone over to Bannon Foods and into the warehouse. We'll land it on the top of one of those big stacks of dry goods, with the camera pointing into the middle of the warehouse. Then we can watch everything they do from the inside, without being there ourselves."

Linden and Willow looked from Elon to the drone and back again.

"The Silver Dragon is pretty noisy," Linden said. "I think they'll hear it coming into the building."

"Did you hear how loud it was when they open and closed the metal doors at the loading dock?"

Linden nodded.

"We just have to fly it in under the cover of a door opening. Once we've landed inside, it'll be silent until we leave."

"I don't know," Willow said, shaking her head. "It sounds crazy. How quickly can we get it in a doorway and land it?"

"We'll have to practice," Elon said.
 

"What about the autopilot?" Linden asked "This is supposed to be an
autonomous
drone."

"The GPS won't work inside," Elon said.

"Dead reckoning?" Willow said. "Can't the motion sensors detect how far it's flown?"

Elon shook his head. "It's not exact. And besides, we don't have a perfect map of the inside of the building."

"What are you saying?" Willow said. "That'll you'll fly it by hand without even being able to see it?"

"We'll have the camera and your laptop," Elon said. "We can fly by watching the video feed."

"The camera's not working yet," Linden said.

"Then we get it to work," Elon said. "You do want to solve this mystery, right? And we built the quadcopter so we could do stuff with it. Imagine how good it'll look at the science fair if we catch a criminal!"

Willow and Linden slowly nodded.
 

"We're going to need supplies," Linden said. "Chocolate chip cookies. Potato chips."

"Root beer," Willow said. "And seaweed."

After they'd stockpiled the necessary nourishments, they all got to work.

Elon worked on mounting the camera, while Linden and Willow worked together on the camera telemetry module, the transmitter that would broadcast live video to Willow's laptop.

Willow and Linden argued over wireless protocols, while Elon placed the camera in a weatherproof housing, then attached it to the frame, where it hung off the leading edge. Staring at the lens, he knew it would unbalance the quadcopter. The autonomous leveler would keep the drone flat, but it'd be less efficient than being balanced. So he hung the drone from a string in the center, and moved the battery pack toward the back until the weight was symmetrical again.

It was hanging nicely from the string, and he was staring straight into the camera, when he noticed himself in a window on Willow's laptop.
 

"It's working!" he cried.

"It's working!" he heard from Willow's laptop a fraction of a second later.

"There's audio, too!" he said in surprise.

"There's audio, too!" came from the laptop.

"One high-def video and audio stream," Linden called.

"Sweet." Elon put one hand on the drone, and turned it slightly so it was pointed out the window. The big Douglas fir in the yard appeared on Willow's laptop. "Are we done?"

"We still need to wire up the avoidance detectors."

The drone had five ultrasonic range finders. Each was accurate to within inches. One faced down, and the others were pointed in each of the four directions. They'd connected the downward-facing range finder so they could maintain a constant altitude. The other four were to make sure the drone didn't crash into anything.

"Do we need them for Monday?" Elon asked.

"Depends," Linden answered, "on whether you want to crash into any forklifts, support poles, or boxes inside the warehouse."

"Good point."

By the afternoon they'd finished wiring it all together. Then they took it for a test flight in the yard with the last light of day. With avoidance detection and stabilization, it was tame enough to control even in their small yard.
 

"Tomorrow we practice flying around obstacles," Elon said.

"More important than that," Willow said, "is that we have to fly using only the video on my camera. You can't be out here where you can see the yard. You've got to do it all using only my laptop."

Elon stared at the screen and thought about the difficulty of controlling the quadcopter when he could see in just one direction at a time. "Oh, snap."

Sunday came in a blink, and they spent the day in a haze of debugging, tuning, and test flights.
 

They set up an obstacle course to mimic what they thought it would be like to fly inside the warehouse. Linden was stationed outside so he could let Elon know if he was about to crash. Willow and Elon set up inside the garage, with the laptop and controller. It turned out they couldn't hear a thing over the drone's audio while it was in flight due to the noise of the rotors, so they used walkie-talkies to communicate.
 

By the end of the day, Elon could fly the copter through the swing set, around the Douglas fir, between the cherry trees, and then land it on top of the minivan in the driveway.

"Ninety seconds," Willow said, shaking her head.

"That's good." Elon shook out his hands, which were shaky and sweating after hours of flights. But he felt confident that he could do it tomorrow.

"Except the loading-bay doors only took like a minute to go up and down, so people are going to hear the buzz. And you've never flown inside the actual warehouse. You knew which way to bank and turn here."

Elon shook his head, afraid he might cry. "I'm doing the best I can!"

"I know, I know," she said, putting her arm around him. "We'll just have to do what we can."

Linden stood in the doorway carrying the quadcopter. "I have an idea. Doesn't Atlanta's dad have an air horn from those races he judged? That could cover up the sound of the Silver Dragon, and maybe distract anyone from looking where it's going."

They all nodded slowly.
 

"That could work," Willow said. She looked outside. "It's getting late. I'd better ride over there right away."

"Wait!" Elon rushed for his camera. "Let's all get a picture with it."

They gathered around the project table, with the Silver Dragon parked on the surface. Willow held her laptop, and Linden the remote control. Elon set the camera for an auto-picture, then ran around and got in the middle, his arms around his siblings. The flash went off with blaze of light, then Elon checked the photo. Perfect!

Willow left in a rush, and Linden and Elon set all the batteries to charge. They packed the Silver Dragon inside a cardboard box, because they'd have to take it on the bus first thing in the morning.
 

When Willow got back with the air horn, she packed her laptop and the remote control.
 

"Basil and Atlanta are almost done with their science-fair project," Willow said. "They've got twenty feet of hair-rope, and they built a wood swing set, so people will be able to sit on it and swing. Even Atlanta's dad sat on it and swung."

"Whoa," Linden said.

"It's gonna be cool," Willow said. "But I'm still glad we worked on the drone. We couldn't be doing what we're going to do tomorrow morning without it. Good idea, Elon."

"Yeah, great idea!" Linden said.

Elon smiled, tired but happy that the autonomous drone worked and their plan to spy on Bannon Foods had come together.

CHAPTER EIGHTEEN

T
HEY
ARRIVED
ONCE
more at the stop near Bannon Foods. Willow's backpack was heavy with her laptop inside its protective sleeve. Linden's bag also sagged under the weight of batteries and controller, while Elon struggled to fit the light but large cardboard box with the drone through the bus's door.
 

They kept to the shadows as they approached Bannon even earlier than they'd ever gotten there before. A long row of trucks were parked in front of the loading bays. But unlike their prior visits, when the parking lot was nearly full, this time there was only one car parked in the lot and the warehouse doors were shut.

"Thank goodness," Linden said. "They do sleep like normal people."

"I'm glad they're not undead," Elon said, "because then they'd never sleep."

Willow shushed them. "We don't want anyone to look up here."

They turned into the property next to Bannon Foods, a small brown industrial building with its own parking lot, where they'd never seen more than a few cars. They found an area on the side nearest Bannon. They set up between two garbage dumpsters, carefully unpacking the Silver Dragon, plugging in batteries, and getting the accessories ready. The backlight off Willow's laptop hurt their eyes in the darkness of the night, so Willow turned the brightness way down.

"It's good for battery life, too."
 

Linden got out the binoculars, laid on his stomach at the edge of the parking lot, and tried to read license plate numbers on the trucks. He couldn't see anything, so he got out his dad's Tiablo flashlight, and focused the narrow beam at the bumper of the first truck. The fancy LED light had a brightness control, so he dialed it down to a mere one percent to start. He had to increase to three percent power before he could see anything, but then the light bounced off the reflective license plate, and he could read it. He went down the line of trucks as fast as he could, knowing that even the tight beam, low-light flashlight would give away his position if anyone looked up. When he got to the fifth truck, the plate matched.

"It's fifth from the left," he explained.

"Got it," Willow said.

Everything was ready, so they turned the drone on, connected the wireless, and checked the video feed on Willow's laptop. Elon overlaid the flight-planning software with a satellite map of the area. He marked their current location. He looked across the lot with binoculars, picked out a flat spot on the roof of Bannon's warehouse, then programmed that location into Willow's computer. He glanced at Willow, who nodded, so he clicked start on the flight plan.

The copter's rotors spun, blades slicing the air with a startling loud whine in the night. Resisting the urge to watch the drone itself, he kept his eyes focused on the screen to watch the video feed from the camera. The drone flew itself toward the warehouse, but Elon kept his hands on the controls, ready to override the autopilot if necessary.

The lights off the Bannon warehouse silhouetted the dark trucks parked in front. The copter flew past a truck, then rose up over the lip of the building roof, and settled down. As soon as the drone landed, Elon cut the throttle to save batteries and avoid noise. From the rooftop, it would be a short, quick flight into the building.

Elon programmed the next set of waypoints, his fingers flying over the keyboard in the darkness. He knew roughly where the pallet racks were inside the warehouse, and he'd only need to take control at the last moment to land.

They didn't have long to wait. Suddenly the far left loading-dock door began to open, a dull roar even at this distance.

"Wait," Willow said. "They'll be looking at that door. Go when the next door starts to open."