Gray craned up at it. Father Giovanni surely knew the significance of the Celtic crosses, how they were modifications of older Druid crosses, which likewise had been borrowed from the ancients who originally occupied the British Isles and carved that symbol on their standing stones. One symbol that linked all three cultures, flowing from the ancient past to the present.

Had the key followed the same path? From ancients, to Celts, to Christians?

Wallace stared across the cemetery. "Father Giovanni measured all the crosses?"

"He did indeed."

"And you said he did the same to some stone ruins?"

"Over this way." Lyle circled the rubble of the abbey bell tower and marched into a grassy field. He kicked his feet as if looking for something. "Father Giovanni searched all the ancient hut circles. Most are on this side of the island."

Wallace marched beside Gray. "No wonder the monks set their abbey here. It was common for the early Church to build on sacred sites. Stamping their religion on top of another. Both as a way of getting rid of it, but also to help the newly converted smoothly transition into the new faith."

"Here!" Lyle called out from a few yards to the right. "I think this is the one!"

Gray crossed over with Wallace. The boy stood in the middle of a crude ring of stone blocks half-buried in the turf. Gray walked its circumference.

Wallace scratched his chin. "Are you sure this is the right hut circle? The one our friend was interested in?"

Lyle suddenly didn't look so certain.

Gray stopped at one of the stones. He knelt down and parted the grasses. He stared down at the stone and knew they were at the right place.

On the crude boulder was carved a symbol.

A spiral.

Gray stared across the field. He double-checked with his compass. In a direct path east from here, where the sun would rise on the new day, stood Lord Newborough's grave marker, a giant Celtic cross, whose roots traced back to the same artisans who had carved the ragged spiral on the boulder at Gray's feet.

"This is it," he mumbled.

"What's that?" Wallace asked, not hearing him.

Gray continued to study the distant cross. He didn't need any measuring tools, though he might not have figured it out so quickly if it hadn't been for Lyle telling him about the painstaking survey the priest had done here.

"I know where Father Giovanni looked," Gray said.

Rachel drew closer. "Where?"

"Between the spiral and the cross," Gray said and pointed to Lord Newborough's grave marker. "Like on the stones up at your excavation, Wallace. Crosses on one side, spirals on the other."

"And like the leather satchel," Rachel reminded him.

Gray nodded. "Though Marco never had that advantage. He had to figure all this out on his own. Going by only what he saw at the excavation site. It must have finally dawned on Marco. Possibly literally. Father Rye said that Marco became agitated last June, which meant he was here during the midsummer solstice. The longest day of the year. A sacred holiday for the pagans, especially those who worshiped the sun."

He pointed to the cross and drew a line down to his toes. "I wager it would take calculations to prove it-something Marco likely did-that on the morning of the solstice, the sun's first rays would strike that cross and cast a shadow pointed straight here."

"And that led to Marco's discovery?" Wallace pressed.

"Maybe. I can pace it out to be sure, but I don't think I have to. Look what sits exactly midway between the cross and the spiral."

Gray pointed at the pile of crumbling stones.

"Saint Mary's tower," Wallace said, then turned to him. "You think whatever Marco found was hidden beneath the tower?"

"You said it yourself. That the Church built its holy buildings atop older sacred sites. The island is riddled with caves. Caves that the Druids considered sacred. And stories continue to this day of some powerful magic, personified by Merlin, buried in a cave on the island. What if they got the cave wrong?"

Wallace's voice grew hushed. "Not the Hermit's Cave, but something hidden in secret under the abbey."

Rachel asked a good question. "But how do you look under there?"

"That dead priest sure didn't bulldoze his way in there," Kowalski added.

They were both right. There were no signs of excavation around the tower ruins.

"There must be another way down there," Gray said and turned to the best source for that information. "Lyle, are there any other tunnels or caves somewhere near here?"

"Aye. Lots of caves. But none too close."

It would take them months to search them all. Gray stared over at Rachel. She stood with her arms crossed. They didn't have months.