shattered cable. âI donât understand. What could have caused this?â Pitt looked thoughtful for a moment. âMy guess is Primacord .â Gunn was stunned. His eyes flew wide behind the big glasses. âYou canât be serious? Isnât that an explosive?â âYes it is,â Pitt said calmly. â Primacord looks like string or rope and can be made in any thickness. Mainly, itâs used for blasting down trees and setting off different groups of distantly spaced explosives at the same time. It reacts like a burning fuse except that it moves and bursts rapidly, almost with the speed of light.â âBut how could anyone plant explosives under the ship without being seen? The water is crystal clear in this area. Visibility is over one hundred feet. One of the scientists or crew members would have seen any intruderâ¦Not to mention hearing the sound of an explosion.â âBefore I attempt to answer that, let me ask you two questions. What equipment was attached to the cable when it parted? And at what time did you discover the break?â âThe cable was connected to the underwater decompression chamber. The divers have been working at one hundred and eighty feet and it has become necessary to begin decompression underwater for long periods of time to prevent the bends . We discovered the broken cable at about 0700 in the morning right after breakfast.â âI take it that you left the chamber in the water overnight?â âNo,â replied Gunn. âItâs our habit to lower the chamber before dawn so itâll be in place and ready to receive the divers in case of an early morning emergency.â âThereâs your answer!â Pitt exclaimed. âSomeone swam under cover of the pre-dawn darkness to the cable and set off the Primacord . Visibility may be one hundred feet after the sun comes up but at night itâs less than one foot.â âAnd the noise from the blast?â âElementary my dear Gunn.â Pitt grinned. âI should guess that a small amount of Primacord detonating at approximately eighty feet of depth would sound very similar to a sonic boom from one of Brady Fieldâs F-105 Starfires.â Gunn looked at Pitt with respect. It was basically a sound theory, and obviously there was little he could think of to debate about. His forehead creased. âWhere do we go from here?â Pitt downed the scotch and banged the glass onto Gunnâs desk. âYou just stay in the briny and fish for your Teaser . Iâm going back to the island and try my hand at a little hunting. There may be a tie-in with your disruptions and the attack on Brady yesterday, and the next step will be to find whoâs behind this mess and what their motives are.â Suddenly the door burst open and a man leaped into the cabin. He wore only a pair of abbreviated swim trunks and a wide belt, containing a knife and a nylon net bag. His wet, sun-bleached hair was streaked with whitish yellow and freckles dotted his nose and chest. As he stood there, the water dripped to the carpet around his feet in spreading dark stains. âCommander Gunn,â he shouted excitedly. âIâve seen one! Iâve actually seen a Teaser, not more than ten feet in front of my mask.â Gunn jumped to his feet. âAre you sure? Did you get a close look at him?â âBetter than that, sir, I took a picture of him.â The freckle-nosed man stood there, grinning with every available tooth. âIf only I had a speargun, I might have got him, but I was shooting coral formations with my camera instead.â âQuick,â snapped Gunn. âGet that film to the lab and have it developed.â âYes sir.â The fellow turned and dashed out of the door, spraying Pitt with a few drops of salt water as he passed. Gunnâs face had a happy but determined look. âMy God. To think I was about to give