The clearing and the hut, with smoke billowing from it, dropped into nothingness. The night enclosed the helicopter-plane. * * * * * From the air, Panama Canal at night is a necklace of lights strung across the thin neck of land that separates sea from sea. Then, as a high-flying plane drops lower, the beams of light loosen into widely separated patches, which are the locks; between them the silky black ribbon of water runs, now widening into a dim, hill-girt lake, now narrowing as it passes through massive Culebra Cut, then widening again as it comes to the artificial Gatun Lake, at the far end of which stands Gatun Dam and its spillway. Silence hung close over the Canal. The last ship had passed through; the planes that daily maneuver over it had returned to their hangars; the men who shepherd ships through the locks had gone either to bed or to Panama City or Colon. The Canal, as always at night, seemed almost deserted. To Chris, clutching tight to his hazardous perch, it looked utterly deserted. The ride had been nightmare-like, fraught every second with peril. Several times the whip of wind had come near tearing him loose; the cold air of the upper layers had numbed his fingers, his whole body; he was chilled and, experiencing the inevitable let-down which comes after a great effort, miserable. Just then, the task ahead appeared well-nigh impossible. The only thing in his favor was that Kashtanov apparently did not know he was aboard, since the plane had flown evenly, steadily, not trying to shake off the man hanging to its landing gear by somersaulting in the sky. Evidently the jolt as it was rising hadn't warned the unseen pilot; the fog from the broken machine had obscured Chris's wild leap. But what, he thought, of that? The element of surprise was in his favor--but how to gain advantage by it? He had no weapon, nothing save bare hands with which to subdue a foe as elusive as the wind that was now hurtling by him. Clinging there, slipping now and again, drenched with cold, the odds looked hopeless. Then, suddenly, the booming of the main motor stopped. Only a quiet purring from the wings took its place. The helicopter-plane hovered almost motionless, quiet and deadly like a sinister bird of prey. It began to drop straight down through the dark. Chris Travers glanced below. * * * * * There, misty, fainty, small as the toy of a child, lay Gatun Dam, with the spillway in its center. Chris stared. So small the dam looked--this dream of an engineer, this tiny outpost of man's genius thrust boldly into the breast of the tropics, holding back a whole lake with its cement flanks, enabling ocean to be linked to ocean! It was the heart of the Canal; if burst, the veins would be drained.