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.

Over the last few centuries we have shot, trapped, and skinned the predators that formerly thrived at the top of the food chain in the wild. Wild bears, wolves, and big cats are all in retreat, and a growing number of scientists are discovering that by eliminating predators, we have changed the environment. Removing predators from the wild has thrown ecosystems off-kilter, triggering domino effects that scientists are just beginning to understand. In "Wild Predator Invasion," NOVA follows scientists who are trying a simple but controversial solution: returning apex predators—like wolves, bears, and panthers—to their natural environments. Can these newly reintroduced predators restore the natural balance of their ecosystems without threatening the humans who live among them?