But if it was merely slippage, Mr. Dunworthy wouldn’t look so utterly devoid of hope. Unless the bomb blast had destroyed his drop.

“Where’s your drop?” she asked, and then remembered what Mr. Humphreys had said about him frequenting the north transept. “It’s here, isn’t it? In St. Paul’s? Is that why you’ve been coming here every day? You’ve been waiting for it to open?”

He shook his head. “It isn’t going to open.”

“What do you mean?”

A horrible thought struck her. He’d been to the Blitz before. What if it had been in February? “Mr. Dunworthy,” she said urgently, “when were you here before?”

“Here we are,” Mr. Humphreys said, arriving with a wooden folding chair. He opened it out with a snap and set it in front of the painting. “Come, sit down.” He took Mr. Dunworthy’s arm.

Mr. Dunworthy sank down heavily onto the chair, and Polly saw with dread how painfully he moved, how frail he was. She’d assumed she’d be killed just before her deadline by a bomb or shrapnel, but there were other ways of eliminating someone who might create a paradox—complications following an injury, or pneumonia.

“I should have thought of this before,” Mr. Humphreys was saying. “There should always be chairs in this bay, so that visitors can sit and contemplate The Light of the World.” He smiled happily up at it. “It’s a painting which cannot be understood in a few moments of looking. It requires time.”

“Time,” Mr. Dunworthy said bitterly.

Oh, God, Polly thought. He does have a deadline.

“Did you tell Mr. Hobbe you were a fellow admirer of The Light of the World, Miss Sebastian?” Mr. Humphreys asked brightly. “That was why I wished the two of you to meet, Mr. Hobbe. I knew I was right to insist on its being here in St. Paul’s, even though only as a copy. ‘It belongs here,’ I told Dean Matthews. ‘Who knows what good may come from some visitor’s seeing it?’ And now look, it’s brought the two of you together. God truly does work in mysterious—”

Mr. Humphreys stopped at a sound of voices and looked out across the nave. The three sailors who’d been in the north transept were looking at the bricked-up Wellington Monument.

“Oh, good, they didn’t leave after all,” Mr. Humphreys said. “If I may take leave of you for a moment, I need to speak with them. I did not finish telling them the story of Captain Faulknor.”

He hurried off. Polly knelt in front of Mr. Dunworthy. “When were you here in the Blitz before?”

“When I was seventeen,” he said. “And again when I was—”

“No, no, the dates. What dates were you here doing observations?”

“In May and in October and November.”

“And that’s all?”

“No,” he said, and she could tell from his face that this was it, the bad news.

Oh, God, she thought.

“September the seventeenth.”

But both that and his assignments to October and November were safely past. Might he have come through early for the May raids to set things up as she’d done for Dulwich? “When did you come through for the big raids?”