I looked around at the others. Everyone was deeply concentrated. Nazari saw me looking and nodded at me. “Yes.”

“Those are the bigger caverns. The excavations. You see the squiggly lines that taper off?”

She nodded again. “Go on, yes.”

“Those are entry points to the system.” I traced a finger along the edge of a large cavern shape. “If you look close you can see that there are actually two systems represented on the map.”

The others leaned over. What they were looking at was a boundary edge, the thin borderline between neighboring cave systems that came close to each other, but didn’t connect.

I turned to Simone. “I believe that’s the reason for the trouble and the attack on your husband. He got too close to what the mayor was doing, and the mayor became paranoid.”

Vaugeois was struggling to make sense of the map. She said, “I don’t understand how you can draw that conclusion from this. It just looks like a bunch of crooked lines drawn on a piece of paper.”

“Watch.” I squared the two maps, one on top of the other, corner to corner. Same size paper. I fastened the big sheets together with a bunch of foldback paper clips from Gilles’ desk drawer. Daniel took one end, I took the other. We moved over to the big window and held the maps up to the light.

The white paper sheets became transparent with the backlight, like tracing paper. Only the drawn lines were visible. We were now able to see the surface map overlaid with the underground map. Like a single unified truth.

I said, “Look where the cavern entrance tapers in.” I was pointing to a part of Brumaire. The cavern shape clearly narrowed to the corridor right in front of Gilles and Simones’ bedroom. The location corresponded perfectly to the entrance to the cave from the house.

Simone inhaled sharply. “Mon dieu.” She was at my shoulder and clutching my arm. “But, Tom, why was the mayor worried about what Gilles might know? What is he doing with his cave?”

“Nothing good, ma’am, that’s for damn sure.”

Nazari said, “That’s what we’re going to find out.”

I looked at Bonnet. He said nothing. I said, “What do you think, Bonnet?”

He licked his lips. “Did you think it might be a good idea to call the police?” He turned to Nazari. “Did you think about including me?”

She said, “There were good reasons not to trust our colleagues, and that included you. It’s all happened fast.”

I said, “Don’t dwell on the past, Bonnet. The mission happens here and now. We have no time to call backup because they are activating an exit strategy as we speak. Now listen up and I’ll tell you what we’re going to do.”

Bonnet shrugged and held his hands up, body language for, ‘okay, no problem.’