“So we’re looking for an airfield near Oxford,” Mike said.

“Or Backbury,” Polly said.

“Or Backbury. And near a railway station, and one that has two words in its name and begins with D, P, T, or B. That narrows it down considerably. Now, if we can just find a map …”

“We’re working on that,” Polly said. “And I’m working on writing down all the raids.” She gave them each a copy of the list for the next week.

“There are raids every night next week?” Eileen said.

“I’m afraid so. They let up a bit in November when the Luftwaffe begins bombing other cities, and later on when winter weather sets in.”

“Later on?” Eileen asked in dismay. “How long did the Blitz last?”

“Till next May.”

“May? But the raids taper off, don’t they?”

“I’m afraid not. The biggest raid of the entire Blitz was May ninth and tenth.”

“That’s when the worst raid was?” Mike asked. “In mid-May?”

“Yes. Why?”

“Nothing. It doesn’t matter. We’ll be out of here long before that.” He smiled encouragingly at Eileen. “All we have to do is figure out where Gerald is. Can you think of anything else he said that might give us a clue? Where were you when you had this conversation?”

“There were two—in the lab, and then over at Oriel when I went there to get my driving authorization. Oh, I remember something he said about that. It began to rain while he was telling me how important and dangerous his assignment was, and he looked up at the sky and held out his hand the way one does to see if it’s really raining, then pointed at my authorization—you know, the printed form one has to fill up for driving lessons. You had one, Polly.”

Polly nodded. “A printed red-and-blue form?”

“Yes, that’s the one. He pointed at it and said, ‘You’d better put that away, or you’ll never learn to drive. Or at any rate, where I’m going you wouldn’t,’ and then he laughed as though he’d said something tremendously clever. He’s always doing that—he fancies himself a comedian, though his jokes aren’t funny in the least, and I didn’t understand that one at all. Do you understand the joke?”

“No,” Polly said, and she couldn’t think of anything the form would have to do with an airfield. “Can you remember anything else he said?”

“Or anything at all about when you were talking to him?” Mike said. “What else was going on?”

“Linna was on the phone with someone, but it didn’t have anything to do with Gerald’s assignment.”

“But it may trigger a memory of the name of the airfield. Try to remember every detail you can, no matter how irrelevant.”

“Like the dog’s ball,” Eileen said eagerly.

“Gerald had a dog’s ball?” Mike asked.

“No. There was a dog’s ball in one of Agatha Christie’s novels.”

Well, that’s certainly irrelevant, Polly thought.

“In Dumb Witness,” Eileen said. “At first it didn’t seem to have anything at all to do with the murder, but then it turned out to be the key to the entire mystery.”