Somehow I don’t think this is the right moment to break in, he thought, and looked studiously up at the Spitfire.

“So did you go with him?” one of the women was asking.

The first woman looked offended. “No. I told him I wasn’t about to fall for an antiquated line of chat like that, and I didn’t intend to go anywhere with him, and a good thing I refused, too. A few moments later his plane took a direct hit. Blown to bits. They couldn’t even make out where it had been. It had vanished without a trace.

“I saved his life,” she said. “I told him that. ‘You should be grateful I’m a good girl,’ I told him. ‘If I weren’t, we’d both be dead.’ ”

“And was he grateful?” the second woman asked dryly.

“I knew a girl who vanished without a trace,” the woman next to her said.

So do I, he thought. And it was clear he wasn’t going to find out whether these women had known Polly just by eavesdropping. He approached them, notebook in hand. “What was her name?” the woman was saying. “It began with an S. You remember, Lowry, she was hit by an HE. Totally vaporized—”

“I’m sorry to interrupt, ladies,” he said. “I’m Calvin Knight. I’m here to do a story on the opening of the exhibition, and I was wondering if I might interview you. You all did war work during World War Two, is that right? Were you all in London?”

“She was,” the white-haired one with the lace collar said, pointing at the one who’d spoken of the girl vanishing without a trace, “and these two”—she pointed at the crone and the one with the photographs—“were WAACs.”

“Women’s Auxiliary Army Corps,” the crone said. “We were radio operators.”

“And what did you do?” he asked the lace-collared one.

“Well,” she said, dimpling, “until just a few years ago I couldn’t tell you. I was in Intelligence.”

“She was a spy,” the crone said. “But I had an even more exciting job. I drove a mortuary van.”

“During the Blitz?”

“No, I’m younger than this lot. I was still at school in Surrey during the Blitz. I didn’t join up till July of ’forty-four.”

Which was too late. Polly would already have been driving an ambulance near Croydon by then. And her deadline would already have passed. “Were the two of you in London during the Blitz?” he asked the WAACs.

“No, we were stationed at Bagshot Park,” the first one said, and the second handed him the snapshot he’d supposed was of her grandchildren. It wasn’t. It was a black-and-white photograph of two slim, pretty girls in uniform, one fair, one dark, perched, laughing, on a tank. “I’m the blonde,” she said, “and that’s Louise.” She pointed at the curly-haired girl perched next to her in the picture and then at her friend.

“That’s you?” he said, staring at the snapshot. The faded, stout old woman in front of him bore no resemblance at all to the vivid, laughing girl in the photograph.