Demonized by ancient sources and portrayed throughout history as a cruel madman -- was Emperor Caligula really insane or just the product of a mad world? He inherited a vast empire, unimaginable wealth and the love of his people, but Caligula's reign descended into paranoia, depravity and full-blown insanity. Using dramatic re-enactments along with expert testimony from a forensic psychologist, NGC investigates: Is there a medical explanation behind his terrifying mind?

• Kieran Bew