Hank Paulson, former master of the universe, sits in a nondescript office in northwest Washington, D.C. He is trying to work on his memoirs, but he is struggling. He doesn't seem like the onetime All-Ivy tackle at Dartmouth, the Harvard M.B.A. who ran Goldman Sachs, the prince of Wall Street who went on to be come secretary of the Treasury. He comes across more like an athlete who has lost a game and can't stop talking about the dropped pass, the missed shot. He is trying to explain the weekend last September when Lehman Brothers went down--and the financial world collapsed.