Bagger waved the boys closer. “To earthquake the ridge.”

“What’s that mean?” Frederick asked.

“I know.” Thomas looked at their crew leader. “We’re not just digging galleries. We’re digging mine chambers.”

Bagger nodded.

Frederick adjusted his glasses. “I don’t understand. I thought you said we’re not mining for coal.”

The mention of coal brought Thomas’s thoughts back to Dover. He remembered watching Dad and James work, carefully pouring black powder into cartridges and inserting the cartridges into drill holes to blast the mine walls. “We’re not,” he answered. “We’re digging mines to charge with explosives”—he locked eyes with Boomer—“beneath enemy lines.”

Stunned by Thomas’s statement, the boys looked to Bagger and the others for confirmation.

“The Germans hold Messines Ridge,” Bagger explained. “They are completely entrenched on the higher ground. Our men don’t stand a chance against such a fortified position. The army is depending on us to end this stalemate. It’s gone on far too long and claimed far too many lives.”

“Their trenches stretch on for miles,” George said. “One mine of explosives isn’t going to break their line.”

“No,” Mole said. “But twenty-four will.”

“We’re digging twenty-four mines?” Frederick asked.

“Us and twenty thousand other tunnelers,” Bagger said. “We’ve got miners and sappers from all over Britain, as well as Canadian and Australian miners helping with the mission.”

“I don’t know about you chaps,” George said, “but I’m not too comfortable putting my life in the hands of a bunch of saps.”

Frederick shook his head. “Sappers are combat engineers,” he said, correcting George before Mole could reply. “They specialize in fortification and demolition, and the British army has the best. We are fortunate to have them overseeing our work.”

“You’re right, Eton,” George said. “We’re so lucky to be digging their tunnels beneath an active battlefield.”

“How close are we?” Thomas asked Mole before Frederick and George could get in yet another squabble.

“The mines have to be dug and packed to blow by early June.”

Thomas paused in his petting of Max, who looked up at him from the comfort of Thomas’s lap. “That’s less than eight weeks away.” Less than eight weeks to finish the mines, which meant less than two months to find James. “Are we using black powder or dynamite?” he asked Boomer, not happy about the prospect of working underground with either of the two unstable explosives, especially in galleries and mines that were periodically shelled with artillery fire.

“Neither. We’re using ammonal. It’s cheaper and more stable.”

“How much?” Thomas asked.

“Close to one million.”

“Pounds?” Thomas asked, unable to hide his shock.

Mole smiled and leaned back in his chair, resting his large feet on the edge of Frederick’s bunk. “The Germans won’t know what hit them.”

“One million pounds?” Frederick asked. “That’s almost five hundred tons of explosives! That’s unheard of!”

“Yes, it is,” Bagger said, “and we want to keep it that way until we blow those mines. If the Germans suspect what we’re up to, they’ll rain hellfire on our heads before we finish digging.”