Hathaway went on. 'He was German, so was the book. He was probably familiar with it. He put the envelope on a prearranged page according to a particular formula that had been picked out. The professor said there was a way to find any formula if you only knew how. Isn't that right. Professor?'

That is right,' said Rodney coldly.

'All right. The librarian knew the formula so she could find the page too. She picks up the cyanide and uses it for the tea. In the excitement, she forgets to close the book-'

I said, 'Look, Hathaway. Why should that little guy be doing this? What's his excuse for being here?'

'He says he's a furrier reading up on moth repellents and insecticides. Now isn't that phony right off. Ever hear anything so phony?'

'Sure,' I said, 'your theory. Look, no one is going to hide an envelope with cyanide in a book. You don't have to find a particular formula or page with an envelope bulging a volume out of shape. Anyone who took the volume off the shelf would find that the book would fall open to the right page automatically. A hell of a hiding place.'

Hathaway began to look foolish.

I drove on pitilessly, 'Besides, cyanide doesn't have to be smuggled in from the outside. They've got tons of it here. They can use it to make snow-slides. Anyone who wants a pound or two can help himself.'

'What?'

'Ask the professor.'

Hathaway's eyes widened and then he fumbled in his jacket pocket and drew out an envelope. Then what do I do with this?'

'What is it?'

He took out a printed page with German on it and said, 'It's the page out of that German volume that-'

Professor Rodney grew suddenly scarlet. 'You tore a page out of Beilstein?'

He shrieked it and surprised the hell out of me. I wouldn't have thought him capable of shrieking.

Hathaway said, 'I thought we could test it for stickum from the scotch tape, or maybe for a little cyanide that leaked out.'

'Give it to me!' yelled the professor. 'You ignorant fool.'

He smoothed out the sheet and looked at both sides as though to make sure that none of the print had been rubbed off.

'Vandal!' he said, and I'm sure that at the moment he could have killed Hathaway and laughed during the entire process.

Professor Rodney might be morally certain of Susan's guilt and so, for that matter, might I. Nevertheless, moral certainty cannot be taken before a jury. Evidence was needed.

So, lacking faith in witnesses, I attacked through the one weakness of any possibly guilty person-the possibly guilty person.

I brought her in to witness the new line of questioning, and if the questioning didn't pin her to her guilt, her own nerves might.

From her appearance I couldn't tell how good that 'might' would be. Susan Morey sat at her desk, hands clasped before her, eyes cold, and the skin around her nostrils tight-looking.

The little German furrier was in first, looking sick with worry. 'I did nothing,' he babbled. 'Please. I have business. How long must I stay?'

Hathaway had his name and vital statistics, so I skipped all that and got to the point.

'You came here a little before two o'clock. Right?'

'Yes. I wanted to know about moth repellents-'

'All right. When you came in you went to the desk. Right?'

'Yes. I told her my name, who I was, what I wanted-' Told whom?' That was the key question.

The little fellow stared at me. He had curly hair and a mouth that fell in as though he were toothless, but that was just appearance, for when he talked, small yellow teeth were plainly visible. He said, 'Her. I told her. The girl sitting there.'

'That's right,' said Susan tonelessly. 'He spoke to me.'

Professor Rodney was gazing at her with a look of concentrated detestation. It occurred to me that his reason for wishing to see justice done quickly might be more personal than idealistic at that. However, that was none of my business.

I said to the furrier, 'Are you sure this is the girl?'

He said, 'Yes. I told her my name and my business, and she smiled. She told me where to find books on insecticides. Then, as I was stepping away, another girl came out from inside there.'

'Good!' I said at once. 'Now here's a photograph of another girl. Tell me, was it the girl at the desk you spoke to and the girl in the photograph who came out of the back room? Or was it the girl in the photograph you spoke to and the girl at the desk who came out of the back room?'

For a long minute, the furrier stared at the girl, then at the photograph, then at me. 'They are alike.'

I swore to myself. The faintest smile had passed over Susan's lips, hovering there a moment before vanishing. She must have counted on this. It was intersession. Hardly anyone would be in the library.

None of them would pay much attention to the librarians who are fixtures like the bookshelves, and if any did, he could never swear which of the Library Twins he had seen.

I knew she was guilty now, but knowing meant nothing.

I said, 'Well, which was it?'

He said, like one anxious to put an end to questioning, 'I spoke to her, the girl right there at the desk.'

'That's right,' said Susan, perfectly calm. 

My hope in her nerves hit bottom.

I said to the furrier, 'Would you swear?' He said at once, 'No.'

'All right. Hathaway, take him away. Send him home.'

Professor Rodney leaned over to touch my elbow. He whispered, 'Why did she smile at the fellow when he stated his business.'

I whispered back, 'Why not?' but put the question to her anyway.

Her eyebrows went up a fraction of an inch. 'I was just being pleasant. Is there anything wrong with that?' She was almost enjoying herself. I could swear to that.

The professor shook his head slightly. He whispered to me again, 'She's not the type to smile at a troublesome stranger. It had to be Louella-Marie at the desk.'

I shrugged. I could see myself bringing that kind of evidence to the Commissioner.

Four of the students were a blank and took up little time. They were engaged in research, they knew what books they wanted, what shelves the books would be on. They went straight there without stopping at the desk. None could say whether Susan or Louella-Marie had been at the desk at any particular time. None had even looked up from their books, to hear them tell it, before the scream roused everything.

The fifth was Peter van Norden. He kept his eyes fixed firmly on his right thumb, which had a badly bitten nail. He did not look up at Susan as he was brought in.

I let him sit awhile and soften up.

Finally I said, 'What are you doing here this time of year? I understand it's between sessions.'

He muttered, 'My Qualifyings are coming up next month. I'm studying. Qualifying examinations. If I pass,

I can go on for my Ph.D., see?'

I said, 'I suppose you stopped at the desk when you came in here.' He mumbled.

I said, 'What?'

He said in a low voice that was hardly an improvement, 'I didn't. I don't think I stopped at the desk.'

'You don't think?'

'I didn't.'

I said, 'Isn't that strange? I understand you're good friends of both Susan and Louella-Marie. Don't you say hello?'

'I was worried. I had this test in my mind. I had to study.

'So you couldn't even take time out for a hello.' I looked at Susan to see how this was going over. She seemed paler, but that might have been my imagination. 

I said, 'Isn't it true that you were practically engaged to one of them?'

He looked up with uneasy indignation. 'No! I can't get engaged before I get my degree. Who told you I was engaged?'

'I said practically engaged.'

'No! I had a few dates, maybe. So what! What's a date or two?'

I said smoothly, 'Come on, Pete, which one was your girl?'