“We’re about five meters below the cathedral. Almost at river level. The tunnel will slope up from here, so all the water will have drained,” said Aya. “Let’s get going.”

​

They followed her up the tunnel. Zac, the tallest of the group, had to stoop. About thirty meters in, the tunnel hit a sharp right bend.

​

“I counted steps, and we should be about even with the cathedral’s north portal. The floor looks wet ahead. Be careful,” said Aya.

​

The floor had sloped upward from the crypt between one and two meters, since they could not see the door when looking back from the bend or the bottom of the tunnel ahead when they entered. 

​

“This feels hard,” said Zac, tapping on a rock at the tunnel’s bend. The day before, Eyrún, Stevie, and Aya had visited the Musée Carnavalet, the museum of Paris, to research the geology around Notre-Dame. While inconclusive, the documents showed that the cathedral sat on alluvial soil not as dense as the quarries farther west but substantial enough to support tunneling.

​

“Granite,” said Eyrún, wiping away the soil and shining her light up close. 

​

“Good. This is probably the foundation of the north bell tower,” said Aya, shining her light toward the cathedral. “Darwin guessed right. The tunnel runs between the main walls of the buttresses.” 

​

Water ripples moved away from her boot as she tapped the ground. She turned her light to the wall, which showed a watermark a few fingers’ width up the side. She began walking, and her boots made a soft, sucking sound against the muddy bottom. About every two meters, they passed more hard rocks. She paused at one.

​

“This is part of the earlier Merovingian church. I’m sure of it. Amazing, I must figure out a way to explain why we should explore it,” she said.

​

“I think that hole in the exhibit wall back there kinda gives it away,” said Zac.

​

“I see an opening,” said Aya, who quickened her pace.

​

“Aya, be careful,” Stevie said.

​

Less than ten meters ahead, Aya stopped and shined her light up into a space that swallowed the beam. She stepped back to allow the others to see a stairwell cut in the wall, braced with wood and paved with marble.

​

Stevie recorded the scene as Aya went up. Darwin followed, one step behind. He counted four steps, then three more that angled as the stairwell turned left ninety degrees. He watched Aya go up six more steps and move into a crouch as they reached a ceiling. They were in a space a little more than a shoulder’s width and as long as a human was tall.

​

The walls gave way to rough-cut marble in a perfect rectangle. The ceiling was of the same marble, but with iron handles mounted in a row at its center point.

“It’s a tomb,” said Aya, grasping one handle. “Won’t budge.”

​

“Let me try,” said Darwin, and they squeezed by each other to swap places.

​

“Don’t break anything,” said Aya.

​

The others crammed into the space at the stairway corner as Darwin sat on the uppermost step and pushed up, his head just touching the slab. The slab moved upward, and a faint light poured in.

​

“Close it! Close it!” Aya said frantically, waving her hands downward.

​

The light shut out as the marble thumped back down. Darwin grabbed his light and slowly moved it around the top steps.

​

“What are you looking for?” asked Eyrún.

​

“Here,” said Darwin, tweezing something between thumb and forefinger. “Look, granite chips. And here.” He pointed to the tomb edge and slab where pieces had flaked off.

​

“This is recent,” said Aya. “Someone came down these steps. Zut alors! We’ve made a mess.”

​

“Merde,” said Darwin, realizing they had rubbed muddy prints over the evidence.

“Doesn’t matter, you guys. They didn’t go out the way we came in,” said Eyrún, backing off the lower step. “The tunnel keeps going this way.”

​

“Wait! Eyrún,” said Darwin, but it was too late. Everyone followed her, and he fell in behind. Ten meters ahead, he watched their lights turn one by one to the right. He rounded the corner, and they halted. Pressing in close behind Aya at the back of the line, he saw the tunnel’s roof drop precipitously.

​

“Where do you think it goes?” asked Stevie.

​

“Aya, how deep is the Seine? I think this goes under it,” said Eyrún.