Part Three recounts the period from 1993 to 1996, when the Unabomber was holding America ransom with a series of increasingly powerful bombs before his arrest in 1996. Kaczynski's brother and sister-in-law reveal the emotional story of how they came to suspect he was the Unabomber, which ultimately led to his arrest.

The final episode of the series examines Kaczynski's trial, with the revelation that he was subjected to a secret psychological experiment as a teenaged student at Harvard, a fact some claim could have been responsible for turning him into the terrorist he became.

Picking up in 1985, Part Two tells the story of how the Unabomber began to ramp-up his terror campaign, claiming his first murder and taunting his FBI pursuers. Kaczynski’s secret journals from his time as a grad student in Michigan reveal the extraordinary moment when his thoughts first turned to murder.

The first episode examines the start of the Unabomber's campaign of terror spanning from 1978 to 1985, and dives into Kaczynski’s childhood to discover what might have made a young mathematical genius with few friends evolve into a sociopathic terrorist.