The stench of wet ash and charred timber hung heavy in the suffocating July air. The insula—a sprawling, seven-story apartment block in the Aventine district—was a smoldering, skeletal ruin. It was the third such building to collapse in a fortnight, and the official reports blamed the shoddy brickwork of cheap contractors and the careless cooking fires of the plebeians. Cassia knew better.
Dressed in the unassuming woolen tunic of a scribe, with her dark hair pulled back severely under a linen palla, Cassia knelt in the soot. At twenty-four, she possessed a mind that could calculate the load-bearing capacity of a vaulted arch at a glance. She was a librator, a master engineer, though Rome’s rigid laws dictated that her brother, a drunken fool, sign his name to all her blueprints.
She ran her soot-stained fingers along a shattered foundational pillar. It was made of Roman concrete—opus caementicium—mixed with volcanic ash from Puteoli. It was designed to withstand centuries, let alone a simple kitchen fire. Yet, the pillar hadn’t just cracked; it had exploded outward.
“You’re trespassing, girl. The site is condemned.”
Cassia flinched, instinctively reaching for the iron stylus hidden in the folds of her tunic. A man stepped through the veil of gray smoke. He wore the heavy leather tunic and brass-trimmed helmet of the Vigiles Urbani, Rome’s firefighters and night watch. He was broad-shouldered and heavily scarred, his eyes the color of a stormy sea, carrying an expression of profound exhaustion.
“I am inspecting the structural integrity for the magistrate’s record,” Cassia lied smoothly, standing up and brushing the ash from her knees.
The Vigiles chuckled, a dry, rasping sound. “The magistrate hasn’t sent an inspector south of the Palatine in three years. Try again. I am Lucius. And you are standing in a graveyard, risking a beating from the Praetorians who are supposed to be guarding this perimeter.”
“Then why aren’t they here?” Cassia countered, her sharp gaze sweeping the deserted street. “Three hundred people died here last night, Lucius. And the Emperor’s elite guard abandons the perimeter? Doesn’t that strike a watchman as odd?”
Lucius frowned, his hand resting on the pommel of his short sword. “Many things in Rome are odd lately. The Emperor plays his lyre while the treasury bleeds. We are told the fires are accidents. We put them out. That is the job.”
“It wasn’t an accident,” Cassia said, kneeling back down. She withdrew a small bronze knife and dug into a crevice in the shattered concrete, retrieving a lump of dark, sticky residue. She held it up. “Pitch. Refined sulfur. And saltpeter. This was packed into the foundational cracks and ignited. The fire didn’t bring this building down. An explosive charge did, designed to look like a collapse.”
Lucius stepped closer, his eyes narrowing as he smelled the sharp, chemical tang emanating from the residue. “Who are you?”
“My name is Cassia. I designed this building.” She swallowed the bitter lump in her throat. “I know its bones. It was murdered.”
Before Lucius could respond, Cassia’s eyes caught a glint of metal beneath a charred wooden beam nearby. She strained to push the heavy timber aside. Lucius, sighing, stepped forward and heaved the beam away with a grunt of effort.
Beneath it lay the body of a man wearing a high-quality crimson tunic, entirely out of place in the slums. His hand was locked in a death grip around a scorched bronze cylinder.
Lucius knelt, forcing the man’s stiff fingers open to retrieve the cylinder. He popped the seal. Inside was a wooden tablet coated in black wax, covered in a frantic, scratched shorthand.
“Greek,” Lucius murmured. “I can’t read it.”
“I can,” Cassia said, taking the tablet. She scanned the jagged stylus marks. Her blood ran cold, the oppressive summer heat vanishing in an instant. “It’s a ledger. A schedule of deliveries from the imperial granaries. But they aren’t delivering grain. They are delivering naptha—Greek fire. And the destinations…” She looked up at Lucius, horror dawning in her eyes. “They are targeting the entire valley. The Subura, the Caelian, the Aventine.”
A heavy, synchronized marching sound echoed from the end of the street. Praetorian Guards, their black plumes nodding, were marching into the ruins, their gladius blades drawn.
“They aren’t here to guard the site,” Lucius said, his voice dropping to a harsh whisper. “They’re here to clean up the evidence.” He looked at Cassia, the cynicism in his eyes replaced by a sudden, fierce resolve. “Run, architect. Now.”
