Michael Frayn's play Democracy, currently playing at Tarragon, is not always easy to follow. For some reason, this doesn't particularly matter. The second political drama set in Berlin in Tarragon's current season chronicles the rise and fall of Willy Brandt, West Germany's charismatic leader from 1969 until 1974, and is crammed full of politicians, spies, treaties and references to the nuances of Cold War-era Germany that may occasionally go over your head. But it......