This was my favorite issue yet of the series. Alternating between the various stories running parallel in the book, the plot is moving quickly towards the moment where everything goes to hell.
Chapter four of this book is a tough nut to crack, perhaps because it is the most straight-forward so far. It features Dr. Manhattan on Mars, recounting his life story. From boyhood, teaching himself to be a watch-maker (Hey there symbolism! Glad you could drop by!) to becoming a physics researcher for the government, to the accident that turned him into something far more than human. 
With the introductions and the world-building of the first two chapters out of the way, chapter 3 kicks the story into high gear. The plot against Dr. Manhattan is put into place, as he is confronted with the information that many of his previous associates have been diagnosed with, or even died from cancer. Manhattan's way of dealing with this information is to freak out on live TV and vanish, first for Arizona and then Mars. His disappearance, literally throws the entire world into havoc. Up until this point, Dr. Manhattan was the ultimate Cold War weapon for the United States, there was no weapon that the U.S.S.R. could produce that could hope to counteract him, so, as we've heard in asides previously in the series, the Russians pretty much had to be happy with saber rattling and accepting whatever America wanted to do. Now, with his disappearance, they immediately invade Afghanistan, with their sights set on quite a bit more. This shows the reader just what the stakes are, for those of us who grew up in the 80's, we all knew that nuclear war was a possibility (hell, a probability depending upon what type of rhetoric Reagan and Thatcher were spouting that particular week), but in the world of Watchmen, it's even far more likely, and closer than ever.
It's Saturday morning, and since it looks like it's going to be a pretty nice day here in the Chicago-land area, I figured I'd start it out with a song. Some friends and I were discussing this article at the AV Club regarding what bands you'd like to see one more time, and I started getting nostalgic for my college days and the music that we would listen to over and over again. And fortunately, it just so happens that Thursday night I had downloaded a new album that sounds exactly like the sort of stuff I would have played over and over back in those days. Well, not just in those days, since I've been listening to The Pains of Being Pure at Heart's self-titled album pretty much constantly and enjoying quite a bit. It's just the perfect type of fuzzy pop magic that I loved then, and I love it now. Here's an appropriate song for the day of the week:
[Edit! You can now click to embiggen!]
Chapter 2 is where the plot, as they say, thickens. The main line of the story is the funeral of the Comedian, as each of the main characters remembers a key moment in their life that involved him, leading us to understand just what kind of a miserable bastard that he truly was. From him almost raping Sally Jupiter in the Minutemen's trophy room, to his murdering the Vietnamese woman he got pregnant during the war, all these terrible acts show us the dark side of America that he had come to represent. These flashbacks also tell us a great deal about the characters themselves. Most interesting is the realization of just how disconnected from humanity that Dr. Manhattan is. After murdering the woman in Vietnam, The Comedian chides Manhattan for imploring him to stop, but doing nothing about it, "You coulda turned the gun into steam or the bullets into mercury...but you didn't do nothin' about it!" The Comedian becomes a character that allows the reader to view each of these heroes in extreme circumstances and gives us a true window into the America of this book.