“And when you saw the key in the museum at Knightstone you had an instinct that it matched!” Hazel was shaking her head. “Extraordinary!”

Lucy caught Finn’s eye. She’d told him the whole story; how she felt Catherine had been trying to show her something when she’d visited Chastleton; how she’d realized the key had been missing from the museum collection and how Catherine had shown her the box the night before. She wasn’t about to tell Hazel that her hunch was based on nothing more than a ghostly premonition, though.

“Given the connection between the Catesbys, Chastleton and Knightstone,” she said, “and the dating of both the key and the box, I thought it was worth considering,” she said.

She saw Finn smother a smile. “Shall we try it?” he asked.

Lucy took the package with the key out of her bag and passed it over to Hazel. “I’d rather you do this,” she said, “if you would.”

Hazel unwrapped the key and for a moment it sat, plain and unprepossessing in the palm of her hand. “I see what you mean,” she said. “It is exactly the right design and age, and it does look the correct size. I wonder...” She slid it into the lock on the wooden box and tried to turn it. “It’s stiff,” she said. “I don’t want to force it. After five hundred years I suppose it’s no wonder.”

Lucy, whose heart had been racing, felt a thud of disappointment. She’d been so sure that this was the box that Catherine had shown her, that she had been meant to find. Were they to be thwarted at the last moment by some ancient rust? But Hazel was opening a drawer in the library table and taking out what looked like a little tube of oil. “This should do the trick,” she said.

“WD-40 Specialist,” Finn murmured.

“Exactly.” Hazel beamed. This time, after some slight jiggling, the key turned. The box opened.

It was lined in black velvet and it was empty.

“Oh!” Lucy said, feeling monstrously disappointed.

Hazel’s smile dimmed at her evident dismay. “But it’s wonderful! The key and the box match!”

“Yes,” Lucy said. “But...” She was remembering Maud Enright’s words: “She said that she had lost her most treasured possession and couldn’t rest until it was found again...” Had that possession been the box—or the key—rather than what was inside?

“Do you mind if I examine it?” Finn asked Hazel. “I’ll be very careful.” He put on a pair of gloves. “I saw something similar at Coughton Court,” he said. “It was a box designed to keep secret correspondence in it and there was a catch—” Gently he pressed the velvet base in one corner. “There,” he finished, as the catch was released, and the base lifted up.

“Oh!” This time it was Hazel who exclaimed. Lucy couldn’t speak.

In the base of the box were two miniature paintings side by side, exquisite little pictures in gold frames that were only slightly tarnished with the passing of the years. Both were of children, one slight and fair with golden curls and pensive blue eyes; the other dark, younger, chubbier in face, little more than a baby.