The records at the Canterlot train station were kept in a small room that was only slightly larger than a broom closet. Somepony had somehow managed to force five filing cabinets and a hanging lamp into the small space. Several papers floated through the air, captured in a lavender field. Twilight flipped through them, searching for Railrider's name.

"This would be so much easier if they had a decent filing system!" she growled in annoyance. "Who's in charge of these, anyway?"

Flash looked up from his own pile of papers, which were spread out on the floor. "Keep looking. That info has got to be here somewhere. It may be the key to all of this."

"Key to all of what?" Twilight asked, still examining the papers. "What are you two—wait, I found it!" She pulled out a paper that listed the trains that left and arrived the station last night.

Phillip took it and looked it over. "Last night, Railrider brought in a cargo train from Vanhoover carrying...oh, this is bad."

"What is it?" Twilight said, looking over his shoulder. "It was a cargo of fertilizer and chemicals."

"But look at the note," Phillip said, pointing.

There was a note written on the page: "Train arrived about twenty minutes late with only four cars (one car missing). Railrider left before he could be debriefed."

"That's it," Phillip said. "That's the missing piece."

"What? What's going on?" Twilight almost shouted, finally allowing her calm facade to break, revealing the monstrous worry that she'd been feeding ever since Flash had told Phillip about the burglaries.

Flash looked at Twilight, his lips thin as he pondered his words. Then he spoke. Twilight didn't know exactly what she was expecting him to say, but it wasn't what he said:

"Somepony's going to bomb Canterlot."

"What? How can you be sure?" she cried.

"It started with the burglaries," Flash explained. "They stole fertilizer, charcoal and soup thickener. The fertilizer contains sulfur and the soup thickener had potassium nitrate. Sulfur, charcoal and potassium nitrate are the ingredients in—"

"Gunpowder!" Twilight cried in alarm.

"Then they stole wiring and clocks—equipment needed for building a bomb," Flash added. "And now this. The fertilizer and the chemicals in the stolen train car are highly explosive."

"And now it's somewhere in Canterlot with a time bomb in it," Phillip said.

Twilight felt the all-too-familiar tug of panic on her mind. "What do we do?! How do we stop it?!"

"We need to get the Guards to search the city," Phillip stated. "Go to Princess Celestia. Tell her what's going on."

Twilight took a breath and nodded. Right. Take control. Make a plan. Save Canterlot. "Flash, you're coming with me," she said, taking his hoof. In a flash of purple light, they both teleported.

"You are sure about this?" Celestia said, her brow creased in worry as she examined Flash and Twilight from atop her throne.

"I'm positive, Your Highness," Flash answered. "There's a bomb somewhere in Canterlot, and it could go off at any moment."

Celestia glanced at Twilight, who confirmed her thoughts and fears with a look. "Then there's no time to waste." She turned to one of the Guards who had been standing, stone-faced and silent, next to her throne. "Summon Captain Polaris."

"Yes, Your Highness," the Guard nodded, dashing out of the throne room.

"We will need a city-wide search, with the entire City Guard," Celestia stated, climbing down off her throne.

"We'll help, Princess," Twilight offered.

"Thank you, Twilight," Celestia nodded.

The Guard returned at that moment. Behind him was a large unicorn stallion with a black coat, a long white mane and tail, and bright blue eyes. On the collar of his polished golden armor was a pair of silver bars, indicating the rank of Captain. His cutie marks were a facsimile of the Big and Small Dipper constellations, the images so realistic they seemed as though actual stars had been plucked from the sky and placed upon his flanks.

Polaris, Captain of the Canterlot City Guard, knelt before Celestia and Twilight and spoke in a deep, even tone. "Your Highnesses. I understand we have a situation."

"A big bomb?" Fluttershy said nervously, shaking in fear. "And we have to go search for it?"

"Hey, don't worry, Fluttershy!" Pinkie Pie grinned, excited as ever. "Think of it as a big game of hide and seek!"

"So what happens when we find it?" Spike asked, hurrying alongside Twilight down the halls of Canterlot Castle.

"We tell a Guard and let them handle it," Twilight said. "Where's Rarity?"

There was the sound of hoofsteps behind them. Rarity appeared, wearing a short-sleeved gray shirt, boots decorated with sapphires, purple saddlebags decorated with her cutie mark, and a wide-brimmed helmet. The others gave her a look. "What? Surely you can't expect me to go searching through Canterlot without being properly dressed for it!" she exclaimed.

Applejack silently spoke for the group by rolling her eyes at the ceiling and shaking her head. The friends entered the courtyard. Captain Polaris was giving instructions to a section of gathered Guards, who stood at attention in rows before him, bedecked in full armor and gear that shone in the afternoon sun.

"Each of you has been assigned a location that we believe is a primary target for the bombing," Polaris declared. His voice was even and calm, but projected powerfully over the crowd. "You need to evacuate and secure the immediate area, then search it top to bottom. Once you find the bomb, call it in and let the bomb squad handle it: do not attempt to defuse the bomb yourselves! Is that clear?"

"YES, SIR!" the gathered Guards shouted as one.

"This is what you're trained for! Go!" Captain Polaris shouted. The Guards marched off in droves, hurrying to their assigned areas.

"Come on, girls!" Twilight called as they each joined a group of Guards.

Flash Sentry was with a group of Pegasi Guards that was headed for the Canterlot Library. The city stretched out before him, the polished ponies stopping their business to stare at the Guards overhead, no doubt wondering what was happening.

Stone-faced, Flash told himself. Give nothing away. They could not afford to cause a panic.

But then, out of the corner of his eye, he spotted something odd. There was a light on in the City Guard precinct headquarters. Specifically, in the laboratory.

And he had a good idea about who was in there. Glancing up to ensure that none of his colleagues had seen him, he dipped down and swooped into the headquarters, quickly weaving his way into the forensic lab.

His suspicions were confirmed. Phillip was bending over a microscope, writing in a notepad beside him.

"You should be with the others," he told Flash without looking up.

"What are you doing?" Flash asked.

"I'm examining the dirt stain that was found on Railrider's body. It could have only come from the murderer." Phillip adjusted the magnification on the microscope. "Shale...granite...basalt..."

"Someplace near water?" Flash pondered.

"Hold on, there's something else..." Phillip squinted through the scope. "Is that...concrete?"

Flash frowned in thought. "A concrete structure near a body of water..."

Phillip looked over a map of Canterlot, which he overlayed with a map of railroad lines and examined carefully. "Here!" he declared, pointing. "The dam on the north side. There's an abandoned supply tunnel leading to it."

"I can be there in less than twenty minutes," Flash declared. Spreading his wings, he grabbed Phillip underneath the forelegs and took off out the back door, rising up into the air. The weight of his armor and Phillip's body barely slowed him down as he made a beeline for the northern section of the city.

Eighteen minutes later, Phillip and Flash were standing on a stretch of train tracks, looking down the abandoned tunnel. The dark cave loomed before them, a pair of old, rusted train tracks leading into it, as inviting as the path into the Everfree Forest. There was a wooden barrier set up before the tunnel that read "DO NOT ENTER" in peeling letters.

"Are you sure about this?" Flash asked.

"This sign's been moved recently," Phillip said, examining the ground. "And somepony recently switched the tracks to go down the tunnel." He took a flashlight out of his vest, strapped it around his neck and turned it on. "Come on!"

He took two steps down the tunnel and realized that Flash hadn't followed him. Turning, he saw that Flash was still standing at the entrance to the tunnel. He stared at the stone mouth, his eyes wide, breathing heavily through clenched teeth as he dug his hooves into the ground.

"Flash?" he called out. Flash didn't respond. Suddenly, Phillip understood: Flash was claustrophobic.

"Flash, it's okay," he said calmly. When that produced no response, he spoke again in a harder, sterner voice. "Hey, look at me, private." With an effort, Flash made eye contact with Phillip.

"You have to decide, right here and now, what is more important: your fear or your duty," Phillip told him. "You worked hard for that armor you're wearing now; you took a vow to defend Equestria. Are you going to let fear—your own emotions—defeat you when you have a chance to live up to that vow?"

Flash looked back at the tunnel, imagining that all of his nightmares were waiting inside it, where he wouldn't be able to fly away from them, where he wouldn't be able to escape.

But then he felt the weight of the armor he wore, and he remembered his training, how he'd fought and sweat to earn the honor of being one of Equestria's soldiers. He'd been trained to not think of fear, to only think of one goal: protecting those weaker than himself. Was a mere tunnel going to force him to go back on his promise?

He took a slow, deep breath and exhaled, imagining that he was expelling his fear from his lungs. "I'm coming."

"I'll be right with you," Phillip said reassuringly, turning back into the tunnel. Flash also turned on the flashlight attached to his shoulder plate and followed.

Instantly, the darkness seemed to close in around his back and sides, sealing him off. He felt its cold embrace and tasted years-old dust in the stale, chilly air and felt a knot of panic rising in the back of his mind, but forced it down, focusing on the light before him. Phillip led him down the tunnel, following the tracks along twists and turns. The only sounds were their own hoofsteps on the packed dirt and the occasional dripping of water.

"Why'd you join the Guard, mate?" Phillip asked, his voice echoing off the tunnel walls.

Flash took a moment to answer. "Well, I grew up in Fillydelphia," he started. "I guess you could say I grew up in the wrong neighborhood; lots of drugs and street crimes around me all my life. I never knew my dad; my mother raised me by herself." He smiled wistfully. "We almost never had two bits to rub together, but she gave me the best she could afford. She taught me that there was a better way for ponies to live. That's what made me want to be a Guard; to give guys who grew up like me hope that they could make something more of themselves instead of standing on the corner, making other ponies sick."

The lamp on his shoulder suddenly flickered, signaling low battery. In the brief darkness, Flash was reminded of his fear. All of a sudden, it felt like the darkness was choking him. He froze, gasping in sudden panic.

"Flash, stay with me," Phillip called out, his voice a lifeline in the sea of black. The light turned back on again, illuminating Phillip, who was giving him a look of concern. Flash took a breath and continued walking.

"Your cutie mark?" Phillip asked.

"I got it in secondary school protecting a younger foal from some bullies," Flash replied, realizing that this wasn't just idle talk; Phillip was trying to keep his mind off the situation at hoof, to keep him calm. "They were trying to force him to try a cigarette, and he was refusing. I told them to stop bothering him and they jumped me."

Phillip glanced back at him. "Admirable."

Flash smirked. "I walked away with a black eye and broken nose. They limped away with worse and never bothered anypony again."

Flash wasn't sure, but he thought he saw Phillip smirk briefly out of the corner of his eye. "What about you?" he asked. "What did—"

Phillip stopped, looking ahead. In the beam of his light, they could see a boxcar on the tracks. "We're right underneath the dam," Phillip said, approaching the boxcar. He carefully examined the door, then slowly opened it. The two ponies shined their lights inside.

The boxcar was filled with metal tanks, cylinders and boxes, all of them labeled "DANGER: EXPLOSIVE. KEEP AWAY FROM HEAT." Placed around the boxcar were several small packages with wires running from them like some bizarre spiderweb. The wires interconnected at another package in the center of the car, with a ticking alarm clock placed on top.

"Looks like we found it," Flash said, somewhat nervously.

"If this goes off, the dam will collapse and flood Canterlot," Phillip stated.

Flash reached up for the radio microphone on his collar. "I'll radio the Guard and—"

"They won't get here in time. The bomb's set to go in a few minutes," Phillip interrupted, climbing into the car. He shone his light on the explosives in the center. "Give me your flashlight."

Flash took his lamp off his shoulder and handed it to Phillip, who placed it on a canister opposite him. "Are you, uh, trained in bomb handling?"

"No. Quiet."

Flash audibly heard his confidence meter hit rock bottom. Phillip stared in silence at the bomb. Flash's eyes went to the clock, which continued ticking towards detonation. Doomsday clock, indeed; this bomb was big enough to destroy a big portion of the dam and flood Canterlot.

"Go," Phillip ordered without looking up. "Get out of here. Save yourself."

Every instinct screamed at Flash to run, to flee to safety. But his hooves refused to move. He realized that he didn't care if he died here in a cold, dark tunnel; this was his place, and he was not going to leave his post.

He stood silent, watching Phillip work, his heart hammering in his chest. Phillip continued to examine the bomb; the clock ticked down mercilessly, second by second.

Then Phillip pulled a pocketknife out of his vest, flicking open the blade. His hoof hovered over the wires, as if in hesitation. Red? Green? Yellow? Black? Flash felt his throat run dry.

Slowly, Phillip selected a black wire and placed the blade against it. A single moment of hesitation more, and he cut the wire.

The clock stopped. Both ponies let out a breath.

"That's that," Phillip said, climbing out of the boxcar. "What say we get out of here?"

"I fully agree to that, sir," Flash said in relief.

Author's Notes:

Long one! Sorry this took so long, I know you all have been looking forward to this. I just wanted to put it all in one chapter.

Finale next.