New York (AP) -- Castmates yelled frantically as Julie Stoffer attempted to unhook Veronica Portillo’s zipline harness while suspended 10 stories in the air. The scene dramatically cut between Portillo screaming for her life and her reality TV co-stars nervously watching from below.

I remember that 2004 episode vividly; I'd never seen the potential for real tragedy on MTV's “The Challenge" before. Considered one of show's greatest moments, that incident, along with plenty of highlights, are relived in the six-part docuseries, “The Challenge: Untold History.”