"Hold on, there " came a sharp challenge from the stairs behind and below me. "What are you doing? And what's that picture doing?" It was one of the Museum's guards. "I was going to ask somebody that same question," I told him as austerely as I could manage. "What about this picture? I thought there was a B cklin hanging here." The guard relaxed. "Oh, I beg your pardon, sir. I thought you were somebody else--the man who brought...