bud's curiosity was instantly aroused. "don't tell me you have a new trick up your nautical sleeve to fox the brungarians?"
tom grinned. "that's the general idea. i hope to give hydrolung divers the same protection that your jetmarine has."
"you mean make them invisible to sonar?"
"yes," tom replied, "and also give them personal spy gear to probe the waters around them and spot an 'undetectable' enemy."
bud whistled. "do that, and i'll say you're really a magician, skipper!"
tom himself transferred the analyzer from the sea hound to bud's jetmarine. on a chance that it might become necessary to operate at greater depths—either in searching for the lost missile or in shadowing the enemy—tom also assigned arv hanson the job of rigging the sea hound and another seacopter with his new inventions.
four crewmen volunteered for the cruise. when the jetmarine was ready, tom and bud exchanged tight handshakes.
"good luck!"
"thanks, tom."
the young inventor waved as bud disappeared down the hatch. as soon as the craft had submerged, tom went back to shopton. that evening the swifts were enjoying a quiet dinner at home when a loud, growling buzz shattered their mealtime conversation.
"oh!" sandy gasped. "the burglar alarm!"
the swifts' house and grounds were protected by a secret magnetic field. any intruder breaking the barrier touched off the automatic alarm system. to avoid the buzzing, the family and their close friends wore wrist watches containing tiny neutralizer coils.
"i'll see who it is," tom said, and hurried to the door, feeling a twinge of apprehension.
was this a new attempt by brungarian agents?
he switched on the porch light and peered out cautiously through the one-way glass pane in the door. a slim, hatless figure in a dark suit was just coming up the steps. tom gave a smile of relief.
it was harlan ames!
"hi, harlan!" tom opened the door before ames had a chance to ring the doorbell. "we heard you coming!"
the security chief was startled when he realized he had activated the alarm system.
"that's strange," he said uneasily. "tom, i wonder if—"
he broke off to dart a quick glance at his wrist. then his face relaxed into a look of chagrin.
"great! i forgot my wrist watch!" he murmured. "haven't visited your house in so long i neglected to wear it."
the other swifts smiled in amused relief, and mrs. swift invited him to join them for dessert. ames, however, declined politely.
"thank you, but i just finished dinner myself," he explained. "i dropped by to—"
once again ames's voice trailed off in midsentence, as he reached into the side pocket of his coat.
"my amulet!" he gasped. "it's gone!"
"are you sure?" tom said with quick concern.
ames nodded as he frantically tried all his other pockets. the electronic amulet to which he referred had been issued to all enterprises personnel and family visitors who used the private gate. the amulets were contained in slender bracelets and were designed to trap radar impulses. this prevented them from showing up as blips on the giant detector radarscope mounted on the main building. the purpose of the scope was to reveal unauthorized visitors or spies.
"my bracelet broke this afternoon," ames said. "i slipped it into my pocket to have it repaired. but it's not there now!"
tom grabbed a flashlight and dashed outside for a hasty check of the walk. ames followed, to look inside his black sedan. but the amulet did not come to light.
"did you go home after you left the plant today?" tom asked.
ames shook his head worriedly. "no, i stopped at a restaurant. mind if i use your phone?"
"go ahead."
the security chief called enterprises and asked his assistant, phil radnor, who was on night duty, to make a thorough search. while awaiting the results, ames also called the restaurant, but learned that no such item had been turned in.
half an hour later radnor called back to report no luck. "the amulet may show up yet, harlan," he said. "but i'll alert the guards at the plant to be on the lookout for an unauthorized visitor."
"thanks, phil." ames hung up and turned away from the telephone with an embarrassed look. "fine example i'm setting as head of plant security," he murmured. "let's hope the amulet wasn't stolen."
excusing themselves from mrs. swift and sandy, tom sr. and jr. retired with ames to mr. swift's study to discuss the news he had brought.
"i had a late call from admiral walter this evening," ames explained. "the navy's getting pretty desperate over that lost missile. they're ready to co-operate with any moves you care to make. i take it you're prepared to carry out a search on your own, tom?"
the young inventor nodded. "yes, as soon as i've perfected all the gear i'll need—which won't be long, i hope."
ames added, unhappily, that certain papers and news commentators had been making snide remarks about the swifts' failure to match the brungarians' submarine achievement.
"i think tom has that situation pretty well in hand," mr. swift remarked with a smile.
tom gave ames a full report on his own apparatus for rendering a submarine invisible to underwater detection. ames grinned at the news. the grin grew even wider as he heard of the successful test of the quality analyzer sonar.
"bud barclay's on his way to the south atlantic right now with a fully equipped jetmarine," tom ended.
the next morning he eagerly tackled the job of adding sonar protection and sonar detection features to his electronic hydrolung. what an amazing fish man the wearer would be, tom thought, if his project succeeded!
it would enable a skin diver to operate indefinitely under water at jet-propelled speed—invisible to enemy "eyes," yet be able to spy out any hostile undersea prowlers, including supposedly "undetectable" submarines!
tom chuckled wryly as he mulled over the difficulties ahead. "bud wasn't kidding when he said it would take a magician!"
besides his mask, electronic breathing device, density-control unit, and ion drive, the wearer would now need at least three major additions—first, sonar-blinding equipment with electronic control; second, amplifying equipment to camouflage the wearer's noise under water; and, third, a portable quality analyzer sonar.
"whew! the miniaturizing job alone will be a king-sized headache!" tom said to himself. "i'd better start with a skin-diving suit made of that molded plastic arv is turning out."
after having some of the tomasite sheathing, with its embedding transducers, sent over from the plastics department, tom cut out a suit from a pattern and welded the seams electronically. he had just finished wiring the control unit when chow wheeled in a lunch cart.
"got some deelicious steak-and-kidney pie today," the cook announced, setting it out.
"swell," tom said absent-mindedly.
chow frowned but left without interrupting the young inventor. twenty minutes later the cook poked his head into the laboratory again. tom had not yet touched his lunch.
"brand my vitaminnies, start eatin', boss!"
"sure, chow."
by this time, however, tom had become so absorbed in the task of assembling some tiny monolithic blocks for the computer circuits of his analyzer, that the lunch remained untasted. when chow returned a third time, tom was startled by his bellow:
"get your nose out o' that work, buckaroo, and eat!"
realizing tom's pie had cooled off, chow had brought another serving, hot from the oven. seeing the stern look on the texan's face, tom burst out laughing and obeyed meekly.
"i declare!" chow chuckled. "one o' these days i'll have to force-feed you if you won't pay no mind to your own nourishment!"
"sorry, old-timer." tom smiled. "sometimes i do get a bit wrapped up, i guess."
hour after hour, tom stayed glued to his workbench, sometimes busy with delicate electronic gear, sometimes lost in thought as he pondered a tricky problem in circuit design. it was long after dark when he drove home from the experimental station, yet he was back on the job in his laboratory early the next morning.
by lunchtime tom had all the apparatus assembled. he was just trying on the plastic suit, with all its accompanying paraphernalia, when chow made his usual appearance.
"great sufferin' snakes!" the cook gasped. "you ain't goin' divin' in that getup, i hope! you look like a christmas tree, boss!"
tom nodded glumly. "know something, chow? that's just what i was thinking myself."
the young inventor's suit was loaded down with the various electronic units and festooned with wires. even taking a few steps around the lab convinced tom that the design was too unwieldy.
"i'd probably either get tangled in seaweed or sink from sheer weight," he muttered.
changing back to his slacks and t shirt, tom began eating abstractedly as chow hovered around.
"if fishes could talk, i reckon you'd scare 'em half to death in that rig!" chow said, trying to cheer tom.
"fish do talk," the young inventor said. "at least they make noises. don't you remember that emergency fish-talk code we used when we were—"
suddenly tom paused, his mouth dropping open. "chow! you've just solved my problem!" he exclaimed.
"i have?" chow goggled at the young inventor.
"you sure have!" tom bounced off his stool and began pacing about. "now, take porpoises. they utter all sorts of sounds—grunts, squeals, jawclaps—and one particularly characteristic sound, like the grating of a rusty hinge."
chow scratched his chin uncertainly. "wal, what about it?"
"suppose i used that rusty-hinge noise to mask the diver's noise." tom turned and stabbed the air with his finger. "i could also use that same sound output as the search pulse for my quality analyzer sonar!"
in this way, tom explained, he could eliminate part of his bulky equipment and do an even better job of making the diver "invisible."
bubbling with enthusiasm, tom decided to buy a live porpoise at once and make an exact recording of its sounds. as soon as he had finished lunch, he put in a number of calls to suppliers of marine specimens. but none could provide a porpoise on short notice.
"guess i'll have to catch one myself!" tom told chow.
he drove out to the airfield and took off in a whirling duck for fearing island. at the base, both mel flagler and zimby cox were eager to accompany the young inventor when he told them about the trip he had in mind.
tom chose the sea hound as the fastest and best suited craft for his purpose. with mel's and zimby's help, he quickly rigged a plastic "tank" in the stern cabin. minutes later, the seacopter zoomed skyward, heading for the florida keys.
the flight was a short one at transonic speed. tom chose a sparkling stretch of open water, a mile or so offshore from a palm-green islet. zimby agreed to stay aboard and tend ship while tom and mel went over the side in hydrolungs.
the two glided about in the translucent blue depths, keeping in close range of each other. the sea was alive with shimmering fish of every hue, darting among the coral. suddenly, as tom veered around to rejoin mel, his eyes widened in horror.
a vicious-looking hammerhead shark was zeroing in, directly behind his friend!
"look out!" tom yelled over his microphone.
