Wade nods, then spits out the stench of the carbide fumes. Only 30 percent of Sarawak’s caves have been surveyed, most of these remaining inaccessible to all but a few of the more experienced guides. When it comes to charting unexplored passages, Wade knows Andrew is second to none, a caver exuding a strong case of “booty scoop lust,” an incurable psychological condition common among “Speleo-boppers.”

Andrew guides the longboat to a ledge, holding it steady so Wade can climb out. “Better put your brain bucket on, lots of loose rock ahead.”

Wade fastens the helmet to his head as Andrew ties one end of a very long coil of rope known as a hog to the boat, tossing the rest over his shoulder. “Stay close. It’ll get a bit narrow. There’s plenty of sharp popcorn sticking out along the walls, so watch your clothes.”

Andrew takes the lead, guiding them through a pitch-dark catacomb. He selects a tight, inclined passage and enters, allowing the hog line to feed out to mark their route. After several minutes of steady climbing, the passage squeezes to a claustrophobic tunnel, forcing them to crawl on all fours.

Wade slips on the wet limestone, tearing the skin along his knuckles. “How much farther?”

“Why? You getting entrance fever?”

“A little.”

“That’s ‘cause you’re a keyboard caver.”

“What’s that?”

“A keyboard caver’s someone who spends more time reading the cavers’ mailing list than actually going—hold on. Whoa, what’s this?”

Wade crawls forward on his belly, squeezing in next to Andrew to take a look.

The tunnel has opened to a massive sinkhole. Looking up, they can see stars still glimmering in the early-morning sky, the surface a good seventy-five feet above their heads. Andrew shines his light below, revealing the bottom of a massive hole, another thirty feet down.

A luminescent amber glow casts bizarre shadows from within the pit.

“Do you see that?”

Wade leans forward to get a better look. “It looks like there’s something glowing down there.”

“This doline wasn’t here earlier this morning. The roof of the cavern must have just collapsed. Whatever’s down there probably fell straight through and landed in that pit.”

“Maybe it’s a car? Someone could be trapped down there.”

Wade watches as his Malaysian guide reaches into his backpack and pulls out a Knobbly Dog, a rope ladder made of a single length of wire, the rungs threaded through the middle.

“What are you doing?”

“Stay here, I’m going to climb down and have a look.” Andrew anchors one end of the ladder to the ledge, then allows the Knobbly Dog to unravel into the dark recesses below.

The sky above has turned gray by the time the spelunker steps down into the pit. The early-morning light barely penetrates the darkness and swirling wisps of limestone dust.