Beneath the streets of Rome lies a city of the dead known as the Catacombs—a labyrinth of tunnels, hundreds of miles long, lined with the neatly laid out tombs of the citizens of ancient Rome. Here, in 2002, maintenance workers fixing a broken water main stumbled upon a previously unknown burial chamber like none other in the complex. It was a mass grave of hundreds of bodies spread across six roughly carved caverns, locked away for nearly 2000 years. Who were these people? And can we discover, after all these centuries, what killed them? Could they be Christian martyrs massacred by the Emperor? Or were they felled by a deadly plague? In “Roman Catacomb Mystery,” NOVA’s forensic investigation follows a trail of ancient clues to uncover new secrets of life, death, and disease in the heyday of a mighty empire.