Chapter 75 - The Black Trench
Ten minutes later, the twin jet-drives of the naval launch slammed us against the churning ice of Lake Superior.
The craft was built for rough littoral waters, its reinforced aluminum hull slicing through two-foot-thick shelf ice like a butcher’s cleaver. Spray flew over the armored canopy, instantly freezing into sheets of milky glass. Inside the heated cabin, the low green luminescence of the tactical radar bathed our faces in an eerie light.
Beside me, Ruby had fallen asleep again, lulled by the violent vibration of the twin turbines. Marilyn held Donald’s leather-bound survey against her lap, tracing the bathymetric maps of the Isle Royale archipelago with a gloved finger.
"There," Marilyn said, pointing to a sharp contour drop on the screen. "The Superior Trench. It drops down to nearly one thousand feet—the deepest water on the entire lake. In 1968, Donald and Arthur used pneumatic tunneling shields from the old iron ranges to bore an adit horizontally into the submerged basalt of the ridge."
"How does a submarine or boat access it?" Thomas asked, cleaning the soot from his hands with a rag.
"They don't access it from the surface," Captain Halloway said, his weathered hands steady on the helm. "There’s a natural sea cavern on the southern shelf of Isle Royale called the Devil's Throat. At high tide, it's completely underwater. But Donald built an air-lock caisson inside the rock. You drive a pressurized craft right into the subterranean pocket, seal the exterior gate, and pump the basin dry. It’s an underground dry dock."
"Contact on radar," Lin announced sharply, pointing to a glowing blip four miles ahead. "It's the *Borealis*. She’s slowing down just off the southwest tip of the island."
"She’s not slowing down," Halloway grunted, squinting through the night-vision scope mounted above the dashboard. "She’s deploying her submersible."
Through the gloom, the dark silhouette of Isle Royale rose out of the frozen lake like a sleeping leviathan. The ancient spruce forests on its ridges stood choked with snow, dark and forbidding against the violet glow of the northern sky. Ahead of us, the *Borealis* was anchored over the deep trench, its deck crane swinging a yellow, twenty-foot deep-sea work sub over the open water.
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Suddenly, an orange flash bloomed from the stern of the trawler.
"Incoming!" Halloway roared, banking the launch violently to port.
