Sam Green and Bill Siegel's film will provoke nostalgia among those who are old enough to remember the late 1960s and early 70s, and astonishment in those who aren't.

It tells the story of the American terrorist group Weather Underground (their name comes, of course, from Bob Dylan's lyric, "You don't need a weatherman to know which way the wind blows").

The group committed a number of crimes throughout the United States in the early 1970s in the cause of World Revolution and also managed to spring LSD guru Timothy Leary from prison. Many Weather Underground members escaped prison because of the illegal methods the FBI used to track them down.

The most notorious act of members of Weather Underground was to blow themselves up while trying to make a bomb in an expensive New York town house in 1970.

All these years later, they recall what motivated them in their quest for revolution. Many of them, while acknowledging that their methods were misguided, would still take the same path if it was offered to them.