Passage after passage, like gaping mouths in the shadows, slipped by. Pitt kept his eyes trained on the ground, analyzing the dark red spots. At the honeycombed intersections he paused briefly, studying the trail. If the blood led up a tunnel and then returned it meant a dead end. Wherever the course indicated a single line he pursued it. His body was aching and his vision was hazy at the outer edges; a bad sign. He was bone tired and felt it to the deadening tips of every nerve ending. Pitt stumbled and would have gone down, but Giordino grabbed his arm in a wrench-like grip, holding him erect.

"Take it easy, Dirk," Giordino said firmly, his voice followed by a faint echo. "No sense in overdoing it. You're not in condition to play All American hero."

"It's not far," Pitt said heavily. "The dog should lie around the next couple of bends."

But the dog was gone. Only the hardened blood pools remained where the great white animal had thrashed out the final moments of life. Pitt stared mutely at the huge stains. The dank odor of blood permeated the passageway, adding to, but not quite overcoming, the musty atmosphere. He vividly re-created the attack in his mind: the dog's gleaming eyes, the leap in the dark, the knife sinking into warm flesh and the agonized animal howl.

"Keep going," Pitt said grimly, all weariness forgotten. "The entrance is only another eighty feet."

They plunged on amid the black depths of the mountain. Pitt didn't bother to watch the blood trail, he knew where he was to the inch: he so thoroughly recalled the feel of the walls and floor that he would have been completely confident of finding the door at a dead run without the flashlight and in absolute darkness. The light in his hand swayed in wild arcs as they pounded along into the modern corridor construction.

Suddenly the Dive Brite's beam probed the massive door, holding it in a dazzling circle of light.

"This is it," Pitt said softly between labored gasps for breath.

Giordino pushed his way past and knelt to the ground, examining the inside bolts. He wasted no time; already his fingers were probing the slight crack that separated the door from the frame molding.

"Goddamn," he grunted.

"What is it?"

"Big sliding latch on the outside. I don't have the equipment to jimmy it from this side."

"Try the hinges," Pitt murmured. He aimed the light toward the opposite side of the door. Almost before he said it, Giordino had snatched a short pointed bar from the flight bag and was prying the long pins from their rusty shafts.

Giordino laid the hinge pins lightly on the ground and let Pitt ease the door open. It swung noiselessly, only an inch, at his touch. Pitt peeked through the widening crack, taking a swift look around, but there was no one in sight, no sound, except their own breathing.