The entire movie is framed around a quote from JFK: "Today, every inhabitant of this planet must contemplate the day when this planet may no longer be habitable. Every man, woman and child lives under a nuclear sword of Damocles, hanging by the slenderest of threads, capable of being cut at any moment by accident, or miscalculation, or by madness." Specific attention is placed on the "accident, miscalculation, or madness" part of the quote, as each makes up one part of the film.
"Madness" comes first, and really is a bit of a sucker punch. The segment explains how nuclear weapons could destroy life as we know it on the planet just because people are crazy enough to use them. The specific examples are terrorists here and the filmmakers show security footage of terrorist attacks to really drive their point home and to make sure you're sufficiently shocked within the movie's first 5 minutes. The segment explains how easy it is to get your hands on some Uranium and how willing people are to supply it to terrorists for a few dollars.
"Accident" comes up next and makes the argument that we're probably all going to get blown up because people are really, really careless. Things like bomber jets accidentally carrying nuclear missiles over the US and random equipment failures are highlighted here. This section drags a bit but is a nice change of pace from thinking that there are monsters out there who would willingly kill millions of people.
"Miscalculation" brings up the rear and ends the movie with a bunch of scenarios (both theoretical and that have actually happened in the past) straight out of the movies WARGAMES. Apparently in 1995, the US set off a missile to test some theories about the Northern Lights that initiated Russia's nuclear retaliation procedures. For some reason Boris Yeltsin never pulled the trigger on unleashing a ton of nuclear weapons on the US, despite pleas from his advisers and every step of the procedure directing him to do so. Crazy.
Aside from a few nitpicks (see below), all of the people interviewed were great (including Tony Blair and Jimmy Carter) and really helped advance the message of the film. It's hard to disagree with the message that all nuclear weapons should be destroyed but it just seems so unlikely to be effective, especially in the face of terrorism. If terrorists somehow got a nuclear bomb made after everybody else got rid of everything, it would just be chaos.
Note: The documentary would've gotten 1/2 star higher had a few of their "experts" been able to properly pronounce the word "nuclear."
Additional Interviews (~40min) - 40 more minutes of interviews with Jimmy Carter, Alan Robock, Martin Sherwin, Roger Mollander and Zbigniew Brzezinski. Carter brings up some interesting points about religion but on the whole, it's 40 minutes that probably deserved to be cut from the film.
Archival Footage (~60 min) - Very cool retro, propaganda documentaries about nuclear weapons. I could watch these for hours.