As the violence increased, the pictures began to get blurry—there had been too much crowd motion for an unsteady hand with a little Kodak—but almost every frame told some recognizable piece of the story. We looked at a man throwing something, both the missile and the man indistinct. In separate prints, Theo had done as good a close-up of both as he could. The missile remained a blur, but the man’s face might be identifiable.

“I think that must have been the Hammer,” I said, looking at a snake-covered forearm pushing Dr. King’s head down. “Dr. King was hit by a brick that day. Maybe Johnny was trying to get him out of the way.”

Harmony Newsome appeared in the next shot, clutching the side of her head. Her hand was covering something round and whitish that seemed to be stuck there. In the next frame, she had crumpled to the ground, the round whitish thing having fallen from her hand. Theo had focused on it and blown it up so we could see it was a ball with spikes of some kind in it.

Following that close-up, we saw a cop in riot gear, squatting to retrieve the spiked ball. In the next frame, he was standing and stuffing the ball into his trouser pocket. Both shots were blurry, but you could still tell what he was doing.

At the next light table, I cried out loud. My uncle Peter, his face in clear focus, was pointing a finger—in congratulation? in admonition?—at the man who’d thrown the missile and who seemed to be clasping his hands over his head in a kind of victory dance. His features were indistinct, but Theo had done his best with different exposures, different croppings. The square jaw and shock of thick, curly hair made me think it was a young Harvey Krumas, but I couldn’t be sure.

“That ball.” I walked back to the light table with shots of Harmony Newsome lying on the ground. “I want to see it as clearly as possible. And the cop. We’ll never see his face, but his badge is turned to the camera. Can you get the badge number?”

Theo had loaded all his different exposures and prints into a computer program. “Always is best to start with negatives,” he said, “but maybe here is enough information to tell us this story.”

Karen and I stood behind him while he fiddled with the images. On the ball, underneath the nails, you could just make out the big swooping F followed by the o. Nellie Fox.