As they chugged painfully slowly through the caverns, Siri’s detective mind had kicked in. He was impressed by the tenacity of Yuki-san, who’d sat in room 4 for three days listening to their deliberations, waiting for the moment to arrive when the Lao announced the location of the treasure. But for such a well-planned surveillance operation there was something lacking. Yes, they’d discussed much of the case when they were together in their room. And yes, it had proven worthwhile to transfer the listening device to their new room after the explosion. But their discoveries and insights weren’t restricted to the bedroom. They’d talked on the balcony, in the boat, in the restaurant, sitting on the dock. Who was to know when and where the ultimate revelation would be revealed? To get full coverage they’d have to have another listening device attached to their clothes or in their bags, or . . . At that point, Siri had leaned into Daeng’s ear and shouted a theory that only she could hear.

They walked by the light of the boat pilot’s flashlight to the square where the village pillar lay on the ground, the concrete smashed. The gold or other precious metal had been removed and the sledgehammers left lying around. On one slab of concrete, the smiling face of baku looked up at them, his tail-end gone. He’d failed to protect the village this time, but his expression suggested all was not lost. Still there was nobody to be seen, not a soul.

“The school,” said Beer.

“I know you’re afraid,” Daeng told him. “You don’t have to come.”

“I do,” said Beer, his voice trembling. “I’m a part of this. I want to see my work through.”

“You’re a saint,” said Daeng.

She went up to him and gave him a hug. Siri joined them but his main objective was not to bond with their guide. It was to remove the pistol from the back of his macramé belt. It was hidden by the tail of his shirt but the doctor had seen its outline when they docked. He held it to Beer’s head and twisted the Vietnamese traitor’s arm behind his back one notch short of snapping it off.

“What? What are you doing?” he asked.

“You could shout to your team at the school for help,” said Daeng. “And they’d probably come to see what’s wrong. But we have a gun now. We could pick them off one by one. I doubt there’d be more than six of them and this is a Makarov PM. If it’s fully loaded, and it feels heavy enough, it contains eight rounds. I could even miss a couple with my first two shots and still leave you without allies.”

“I don’t understand,” said Beer.