“Sherry, thank you,” I said.

Mrs. Bittner poured two glasses of sherry and turned to hand them to us. “It caused an incongruity, didn’t it?”

I took the glasses from her, handed one to Verity, and sat down beside her. “Yes,” I said.

“I was so afraid it had. And when James told me last week about the theory regarding nonsignificant objects being removed from their space-time location, I knew it must have been the bishop’s bird stump.” She shook her head, smiling. “Everything else that was in the cathedral that night would have burned to ashes, but I could see by looking at it that it was indestructible.”

She poured herself a glass of sherry. “I tried to undo what I’d done, you know, but I couldn’t get the net to open, and then Lassiter — that was the head of faculty — put on new locks, and I couldn’t get into the lab. I should have told James, of course. Or my husband. But I couldn’t bear to.” She picked up the glass of sherry. “I told myself the net’s refusing to open meant that there hadn’t been an incongruity after all, that no harm had been done, but I knew it wasn’t true.”

She started for one of the chintz-covered chairs, moving slowly and carefully. I jumped up and took the glass of sherry for her till she had sat down.

“Thank you,” she said, taking it from me. “James told me what a nice young man you were.” She looked at Verity. “I don’t suppose either of you have ever done something you were sorry for afterward? Something you’d done without thinking?”

She looked down at her sherry. “The Church of England was shutting down the cathedrals that couldn’t support themselves. My husband loved Coventry Cathedral. He was descended from the Botoner family who built the original church.”

And so are you, I thought, realizing now who it was Mary Botoner had reminded me of, standing there in the tower arguing with the workman. You’re a descendant of the Botoners, too.

“The cathedral was his life,” she went on. “He always said that it wasn’t the church building that mattered, but what it symbolized, yet the new cathedral, ugly as it was, was everything to him. I thought if I could bring back some of the treasures from the old cathedral,” she said, “it would be good publicity. The tourists would flock to see them, and the cathedral wouldn’t have to be sold. I thought it would kill my husband if it had to be sold.”

“But hadn’t Darby and Gentilla proved it was impossible to bring things forward through the net?”

“Yes,” she said, “but I thought since the things had ceased to exist in their own space-time, they might come through. Darby and Gentilla had never tried to bring through anything that didn’t still exist in its own time.” She twisted the stem of the glass in her hands. “And I was fairly desperate.”

She looked up. “So I broke into the lab late one night, went back to 1940, and did it. And the next day, James telephoned to tell me that if I wanted a job, that Lassiter had authorized a series of drops to Waterloo, and then he told me—” She stopped, staring into the past. “—he told me that Shoji had had a breakthrough in temporal theory, that he’d discovered why it was impossible to bring things forward through the net, that such an action would cause an incongruity that could change the course of history, or worse.

“So you tried to take it back?” Verity said.

“Yes. And I went and saw Shoji and made him tell me as much as I could about incongruities without making him suspicious. It was all bad, but the worst was that he told me they’d been able to adapt the net to safeguard against them, and weren’t we lucky one hadn’t happened before we did, we could have caused the collapse of the entire space-time continuum.”

I looked over at Verity. She was watching Mrs. Bittner, her beautiful face sad.

“So I hid the swag, as they say in the mystery novels, and waited for the world to end. Which it did. The cathedral was deconsecrated and sold to the Church of the Hereafter and then turned into a shopping center.”

She stared into her sherry. “The irony is that it was all for nothing. My husband loved Salisbury. I had been so convinced that losing Coventry Cathedral would kill him, but it didn’t. He truly meant that about churches being only a symbol. He didn’t seem to mind even when they built a Marks and Spencer’s on the ruins.” She smiled warmly. “Do you know what he said when he heard Lady Schrapnell was rebuilding the old cathedral? He said, ‘I hope this time they get the spire on straight.’ ”

She set her glass down. “After Harold died, I came back here. And two weeks ago James telephoned and asked me if I could remember anything about the drops we’d done together, that there was an area of increased slippage in 2018, and he was afraid it was due to an incongruity. I knew then it was just a matter of time before I was found out, even though he had the wrong incongruity.” She looked up at us. “James told me about the cat and Tossie Mering. Did you manage to get Lady Schrapnell’s great-great-grandmother married to the mysterious Mr. C?”

“Not exactly,” I said. “She did marry him, but it was no thanks to us.”

“It was the butler,” Verity said, “under an assumed name.”

“Of course,” Mrs. Bittner said, clapping her veined hands together. “The old solutions are always the best. The butler, the case of mistaken identity, the least likely suspect—” She looked at us both meaningfully, “—the purloined letter.” She stood up. “I hid it in the attic.”

We started up the stairs. “I was afraid moving it might make things worse, she said, taking the steps slowly, “so I left the loot here when we went to Salisbury. I made certain it was well-hidden, and I took care to rent the house to people without children — children are so curious, you know — but I was always afraid someone would come up here and find it and do something that would change the course of history.” She turned back, holding onto the banister, and looked at me. “But it already had, hadn’t it?”

“Yes,” I said.

She didn’t say anything more. She seemed to be concentrating all her effort on climbing the stairs. When we reached the first floor, she led us down a corridor past a bedroom and opened a narrow door onto another, steeper flight of stairs. “This leads up to the attic,” she said, panting a little. “I’m sorry. I need to rest a bit before going on. There’s a chair in the bedroom.”

I ran to fetch it, and she sat down on it. “Would you like a glass of water?” Verity asked.

“No, thank you, dear,” she said. “Tell me about the incongruity I caused.”

“You weren’t the only person who considered the bishop’s bird stump indestructible,” I said. “So did the chairman of the Flower Committee named—”

“Delphinium Sharpe,” Verity said.

I nodded. “She had been there the night of the raid, standing guard by the west door, and she knew the bishop’s bird stump couldn’t have been carried out. When it wasn’t found in the rubble or among the things the fire watch had saved, she concluded it had been stolen some time before the raid and that the thief must have known about the raid in advance, knowing he could get away with it. She was quite vocal with her theory—”

“She even wrote a letter to the editor of one of the Coventry papers,” Verity put in.

I nodded. “This next part is only a theory, like Miss Sharpe’s,” I said. “The only evidence we have is Carruthers’s testimony, the list of ladies’ church committees for 1940, and a letter to the editor that wasn’t in either of the Coventry papers.”

Mrs. Bittner nodded sagely. “The incident of the dog in the nighttime.”

“Exactly,” I said. “The Nazis made it a practice to obtain and read Allied newspapers, looking for any intelligence information that might be inadvertently revealed. I think Miss Sharpe’s letter and the words ‘advance warning of the raid’ must have caught the eye of someone in Nazi intelligence who was worried about the Nazi code system being compromised, and that inquiries were subsequently made, inquiries that revealed the High Command had dispatched RAF fighters to Coventry that night and had attempted to jam the pathfinder beams.”