A handful of tourists paused as Max took the stage. “In just a few minutes, a beam from the sun will shine through a tiny hole in the window up there”—he raised his finger—“and hit the floor at this place, as it has every Midsummer’s Day.” He gestured at the metal talon, and continued: “You can see this concave mirror has been placed so it can direct the light through the crystal we have clamped, there.” He squatted to demonstrate the objects with all the esprit of an apprentice television presenter, and Grace and Lucy exchanged amused glances. Max warmed to his task.

“Dr. Dee’s small crystal will divide the beam,” he said, pointing at it, “then one section of it will bounce off this mirror and light up the white card—which is here. The other part of the light will bounce from the other mirror, there, onto this plate, which may have been hand-crafted hundreds of years ago by the artist Dürer. It’s called ‘three.’ We need a bit of luck”—Max laughed—“but if we’ve got the measurements right, it should hopefully create an image of the angel, which will float in midair in front of the card.”

Lucy was getting tangled, and laughed aloud—Max’s grasp of science almost eclipsing her own. She wondered if a preoccupied Alex had slightly denied the little boy some of his childhood, and made a note to herself to bake with him and ride bikes as often as possible.

“The equipment you can see here has just been found among a collection of things from the sixteenth or seventeenth century. Today a laser beam would be better than the sunlight, and the image would be a photographic hologram. But we want to see if we can get any kind of result from the sunbeam. Watch! It should happen any second.”

The dot of light from the sun moved over the floor in the heavy gloom of the aisle until it struck the refracting mirror. For a fleeting moment—literally seconds—the watery image of the angel, first seen in the former front banqueting room of the White Hart Hotel on St. George’s Night, two months before, reappeared to the enchantment of the group. It lacked the definition it had attained in its first incarnation, when Alex had used lasers and prisms in pitch-darkness, but the effect was tantalizing. “Lucy as an angel” appeared and disappeared in the south transept of Chartres Cathedral as the sun crossed the meridian and moved on, repeating a journey that had been similarly noted on this spot—sans angel—for hundreds of years. Gentle applause, which was thought not too boisterous for the religious setting, accompanied the vision.

“Not angles, but angels,” Alex repeated.

Unrelated observers left, but Amel Azziz—who had arrived with Zarina Anwar via Eurostar in time to watch—twinkled at Max. It was obvious that the boy had been brilliantly rehearsed by his father, but nevertheless he was impressed. Now he humorously countered Grace—who had made an offer to the child of an immediate job in television—with a suggestion of his own: that Max come and learn beside him in the operating room in the “proper medical field” of myocardial surgery. Alex laughed at the pair of them.