It took them fifteen minutes to climb past the midpoint, onto the cream-colored ice. The sun came from behind low gray clouds and lit up the frozen waterfall at a sharp angle, pinning him on a wall of translucent gold.

He waited for Tilde to tell them she was over the top and secure. Franco gave his laconic reply. Mitch wedged his way between two columns. The ice was indeed unpredictable here. He dug in with side points, sending a cloud of chips down on Franco. Franco cursed, but not once did Mitch break free and simply hang, and that was a blessing.

He fronted and crawled up the bumpy, rounded lip of the waterfall. His gloves slipped alarmingly on runnels of ice. He flailed with his boots, caught a ridge of rock with his right boot, dug in, found purchase on more rock, waited for a moment to catch his breath, and humped up beside Tilde like a walrus.

Dusty gray boulders on each side denned the bed of the frozen creek. He looked up the narrow rocky valley, half in shadow, where a small glacier had once flowed down from the east, carving its characteristic U-shaped notch. There had not been much snow for the last few years and the glacier had flowed on, vanishing from the notch, which now lay several dozen yards above the main body of the glacier.

Mitch rolled on his stomach and helped Franco over the top. Tilde stood to one side, perched on the edge as if she knew no fear, perfectly balanced, slender, gorgeous.

She frowned down on Mitch. “We are getting later,” she said. “What can you learn in half an hour?”

Mitch shrugged.

“We must start back no later than sunset,” Franco said to Tilde, then grinned at Mitch. “Not so tough son of a bitch ice, no?”

“Not bad,” Mitch said.

“He learns okay,” Franco said to Tilde, who lifted her eyes. “You climb ice before?”

“Not like that,” Mitch said.

They walked over the frozen creek for a few dozen yards. “Two more climbs,” Tilde said. “Franco, you lead.”

Mitch looked up through crystalline air over the rim of the notch at the sawtooth horns of higher mountains. He still could not tell where he was. Franco and Tilde preferred him ignorant. They had come at least twenty kilometers since their stay in the big stone Gaststube, with the tea.

Turning, he spotted the orange bivouac, about four kilometers away and hundreds of meters below. It sat just behind a saddle, now in shadow.

The snow seemed very thin. The mountains had just passed through the warmest summer in modern Alpine history, with increased glacier melt, short-term floods in the valleys from heavy rain, and only light snow from past seasons. Global warming was a media cliche now; from where he sat, to his inexpert eye, it seemed all too real. The Alps might be naked in a few decades.

The relative heat and dryness had opened up a route to the old cave, allowing Franco and Tilde to discover a secret tragedy.

Franco announced he was secure, and Mitch inched his way up the last rock face, feeling the gneiss chip and skitter beneath his boots. The stone here was flaky, powdery soft in places; snow had lain over this area for a long time, easily thousands of years.

Franco lent him a hand and together they belayed the rope as Tilde scrambled up behind. She stood on the rim, shielded her eyes against the direct sun, now barely a handspan above the ragged horizon. “Do you know where you are?” she asked Mitch.

Mitch shook his head. “I’ve never been this high.”

“A valley boy,” Franco said with a grin.

Mitch squinted.

They stared over a rounded and slick field of ice, the thin finger of a glacier that had once flowed nearly seven miles in several spectacular cascades. Now, along this branch, the flow was lagging. Little new snow fed the glacier’s head, higher up. The sun-blazed rock wall above the icy rip of the bergschrund rose several thousand feet straight up, the peak higher than Mitch cared to look.

“There,” Tilde said, and pointed to the opposite rocks below an arete. With some effort, Mitch made out a tiny red dot against the shadowed black and gray: a cloth banner Franco had planted on their last trip. They set off over the ice.

The cave, a natural crevice, had a small opening, three feet in diameter, artificially concealed by a low wall of head-size boulders. Tilde took out her digital camera and photographed the opening from several angles, backing up and walking around while Franco pulled down the wall and Mitch surveyed the entrance.

“How far back?” Mitch asked when Tilde rejoined them.

“Ten meters,” Franco said. “Very cold back there, better than a freezer.”

“But not for long,” Tilde said. “I think this is the first year this area has been so open. Next summer, it could get above freezing. A warm wind could get back in there.” She made a face and pinched her nose.

Mitch unslung his pack and rummaged for the electric torches, the box of hobby knives, vinyl gloves, all he could find in the stores down in the town. He dropped these into a small plastic bag, sealed the bag, slipped it into his coat pocket, and looked between Franco and Tilde.

“Well?” he said.

“Go,” Tilde said, making a pushing motion with her hands. She smiled generously.

He stooped, got on his hands and knees, and entered the cave first. Franco came a few seconds later, and Tilde just behind him.

Mitch held the strap of the small torch in his teeth, pushing and squeezing forward six or eight inches at a time. Ice and fine powdered snow formed a thin blanket on the floor of the cave. The walls were smooth and rose to a tight wedge near the ceiling. He would not be able to even crouch here. Franco called forward, “It will get wider.”

“A cozy little hole,” Tilde said, her voice hollow.

The air smelled neutral, empty. Cold, well below zero. The rock sucked away his heat even through the insulated jacket and snow pants. He passed over a vein of ice, milky against the black rock, and scraped it with his fingers. Solid. The snow and ice must have packed in at least this far when the cave was covered. Just beyond the ice vein, the cave began to slant upward, and he felt a faint puff of air from another wedge in the rock recently cleared of ice.

Mitch felt a little queasy, not at the thought of what he was about to see, but at the unorthodox and even criminal character of this investigation. The slightest wrong move, any breath of this getting out, news of his not going through the proper channels and making sure everything was legitimate…

Mitch had gotten in trouble with institutions before. He had lost his job at the Hayer Museum in Seattle less than six months before, but that had been a political thing, ridiculous and unfair.

Until now, he had never slighted Dame Science herself.

He had argued with Franco and Tilde back in the hotel in Salzburg for hours, but they had refused to budge. If he had not decided to go with them, they would have taken somebody else — Tilde had suggested perhaps an unemployed medical student she had once dated. Tilde had a wide selection of ex-boyfriends, it seemed, all of them much less qualified and far less scrupulous than Mitch.

Whatever Tilde’s motives or moral character, Mitch was not the type to turn her down, then turn them in; everybody has his limits, his boundary in the social wilderness. Mitch’s boundary began at the prospect of getting ex-girlfriends in trouble with the Austrian police.

Franco plucked a crampon on the sole of Mitch’s boot. “Problem?” he asked.

“No problem,” Mitch replied, and grunted forward another six inches.

A sudden oblong of light formed in one eye, like a large out-of-focus moon. His body seemed to balloon in size. He swallowed hard. “Shit,” he muttered, hoping that didn’t mean what he thought it meant. The oblong faded. His body returned to normal.

Here, the cave constricted to a narrow throat, less than a foot high and twenty-one or twenty-two inches wide. Angling his head sideways, he grabbed hold of a crack just beyond the throat and shinnied through. His coat caught and he heard a tearing sound as he strained to unhook and slip past.