Staring with Costigan into the plate, Bradley and the girl saw, not the Nevian sky-rover they had expected, but a fast submarine cruiser, manned by the frightful fishes of the greater deeps. It was coming directly toward the lifeboat, and even as Costigan hurled the little vessel off at an angle and then sped upward into the air, one of the deadly offensive rods, tipped with its glowing ball of pure destruction, flashed through the spot where they would have been had they held their former course. But powerful as were the propellant forces of the lifeboat and fiercely though Costigan applied them, the denizens of the deep clamped a tractor beam upon the flying vessel before it had gained a mile of altitude. Costigan aligned his every driving projector as his vessel came to an abrupt halt in the invisible grip of the beam, then experimented with various dials. "There ought to be some way of cutting that beam," he pondered audibly, "but I don't know enough about their system to do it, and I'm afraid to monkey around with things too much, because I might accidentally release the screens we've already got out, and they're stopping altogether too much stuff for us to do without them right now." He frowned as he studied the flaring defensive screens, now radiating an incandescent violet under the concentration of forces being hurled against them by the warlike fishes, then stiffened suddenly. "I thought so--they _can_ shoot 'em!" he exclaimed, throwing the lifeboat into a furious corkscrew turn, and the very air blazed into flaming splendor as a dazzlingly scintillating ball of energy sped past them and high into the air beyond. Then for minutes a spectacular battle raged. The twisting, turning, leaping airship, small as she was and agile, kept on eluding the explosive projectiles of the fishes, and her screens neutralized and re-radiated the full power of the attacking beams. More--since Costigan did not need to think of sparing his iron, the ocean around the great submarine began furiously to boil under the full-driven offensive beams of the tiny Nevian ship. But escape Costigan could not. He could not cut that tractor beam and the utmost power of his drivers could not wrest the lifeboat from its tenacious clutch. And slowly but inexorably the ship of space was being drawn downward toward the ship of ocean's depths. Downward, in spite of the utmost possible effort of every projector and generator; and Clio and Bradley, sick at heart, looked once at each other. Then they looked at Costigan, who, jaw hard set and eyes unflinchingly upon his plate, was concentrating his attack upon one turret of the green monster as they settled lower and lower. "If this is ... if our number is going up, Conway," Clio began, unsteadily. "Not yet, it isn't!" he snapped. "Keep a stiff upper lip, girl. We're still breathing air, and the battle's not over yet!"