We pause to cross the street. I’ve allowed him to choose the route; I mean he’s the one who lives here, after all, the one who understands not just the map of London but the habits of the place. A couple of bicycles approach, one after the other, and while we wait for them to pass, Mr. B— speaks again.

“Mind you, it was quite against the rules.”

“What? What’s against the rules?”

Mr. B— stares not at my face, but along a line that passes right above my head, down the street to the approaching bicycles. “Marrying,” he says blandly.

The bicycles pass. We cross the street to enter a foggy square of red brick and white trim. Several of the houses are missing, simply not there, like teeth pulled from a jaw. Mr. B— leads me to the gardens in the middle, where we choose a wooden bench and sit about a foot apart, so that our arms and legs aren’t in any danger of touching, God forbid. The button at the wrist of my left-hand glove has come undone. I attempt to refasten it, but my fingers are too stiff.

“Of course, I quite understand your distress, Mrs. Thorpe,” he says, in the voice you might use to console a child. “It’s for that reason that we tend to discourage men such as Thorpe from forming any sort of personal attachment. To say nothing of marriage.”

“We’re all human, Mr. B—.”

“Still, it’s unwise. And then to allow you any hint of his purpose there in the Bahamas—”

“Oh, believe me, he never said a word about that. I was the one who put two and two together. I was on the inside, you see. A friend of the Windsors.”

“Were you really? Remarkable. Although I suppose . . .” He reaches into the pocket of his coat, brushing my arm with his elbow as he manipulates his fingers inside. He draws out a familiar white envelope. I recognize it because I carried this envelope myself, in a pocket next to my skin, for the entirety of the thirty-nine hours it took to cross the Atlantic, from Nassau to London, in a series of giant, rattling airplanes, before I stamped the upper right corner and posted it from a red metal postbox yesterday evening. And it’s funny, isn’t it, how a letter you mailed with your own two hands no longer belongs to you, once it begins that fateful drop through the slot. I glimpse my own handwriting, the stamp I placed there myself, and it’s like being reunited with an estranged child who has grown into adulthood.

“You suppose?”

Mr. B— taps the edge of the envelope against his knee. “I suppose it depends on what one means by friendship.”

“In wartime, friendship can mean anything, can’t it?”

“True enough. This note of yours. Quite astonished me this morning, when my secretary delivered it to my desk.”