So I started out with more assurance, but I took the precaution to act like an onlooker by glancing up over my shoulder now and then at the airborne maelstrom. As I got to the other side of the open space, I had another shock. A few yards ahead was another group of policemen, one of whom, I saw with dismay, was the lieutenant from Charles Street, and he was beginning to turn around. I barely had time to duck into a doorway to avoid being seen. I had the feeling of a member of the I.R.A. in Dublin during the Troubles, and I crouched against the door. I could now hear the lieutenant's voice: "Of course he's up there! Maddigan'll be here with a warrant any minute now and we'll ...." His voice faded away. * * * * * Behind me, the door suddenly opened and I almost fell. A young student holding some notebooks emerged. "Sorry," he said, and walked toward the crowd. The door had not yet closed and I slipped in, with my heart irretrievably contracted to the size of a buckshot. I could just make out in the dim light that I was at the bottom of the fire stairs, so I climbed to the third floor and went into a classroom, then on into an office somewhat like McGill's, that faced toward the lab building. From here, I had a perfect view of the crowd, the police, the upper facade of the labs, brightly lit by the searchlight and, over all, the spinning papers and dust, which even as I looked began to die down. I was unable to see Molly or McGill and wondered whether they had noticed my absence and were worrying. I saw a phone on the desk at my side and considered calling up McGill's office, but first I wanted to think over my new idea. I pulled down the shades and turned on the reading lamp, by the light of which I re-examined the fragment I had been carrying around all day. It sparkled brilliantly. On the desk, beside an onyx pen-set, a golf trophy and a signed golf ball, was a leather-framed photograph of a blank-faced young woman holding a pudgy little boy. I picked it up and rubbed the glass with the tiny fragment. It left a faint but undeniable scratch. So I was right about one thing. Then I called McGill's office. In a few moments, I heard the receiver lifted, but no voice. "This is the nucleus," I said, and I heard of sigh of relief from McGill. "Where in hell are you?" "Across the way. Look, out of your window and I'll turn my light off and on again." I did so. "You're in Professor Crandal's office. Why did you leave?" "We'll go into that later. McGill, that fragment is a diamond." "What!" "At any rate, it scratches glass." "Why didn't you tell me that before? And where is it? I couldn't find it anywhere." "I was sidetracked. I've got it here. Now my idea--" "A diamond! I begin to see light. Give with the idea, Alec."