random hunches and circuit diagrams flashed through tom's brain. "the job will boil down to blotting out sonar waves and piercing the enemy's own 'wave-trap defense,'" the young scientist concluded.

as tom struggled with the problem, he lost all track of time. a door swung open and high-heeled boots clumped on the floor tiles. tom looked up and saw the portly, aproned figure of chow winkler entering.

"hi, boss! can i borrow a radio?" chow asked. "kinda like a lil music while i wrassle them pots an' pans in the galley."

"sure, pardner." tom pointed toward a portable radio on a shelf nearby.

chow's leathery face broke into a grin as he picked it up. "one o' them slick lil transistor doodads, eh?"

the cook flicked on the dial knob and the twangy strains of hawaiian guitar music came throbbing out. a split second later the volume swelled as the same music echoed back to them from the two-room apartment adjoining the lab, where tom ate and slept when engaged in some round-the-clock experiment.

chow was startled by the blare. "you got a stereo hookup here, boss?" he inquired.

"not exactly." tom explained that the music had merely been picked up by the mike on his workbench, then fed into the adjoining apartment and amplified over a speaker there.

chow grinned, snapping his fingers to the catchy melody. "comes out even louder'n it does from the radio!"

"yes, but the sound quality's not so good," tom said. "you'd notice the difference with real stereo."

chow walked out with the portable, crooning contentedly to the music.

tom frowned, trying to get his train of thought to focus once more on the submarine problem. but for some reason the business with the microphone and the speaker in the next room kept lingering in his mind.

suddenly tom exclaimed aloud, "say! i wonder if that's how the enemy sub blinds our sonar?"

the idea certainly seemed feasible. suppose the submarine used a great many "microphones"—or receiving transducers—to pick up the sonar pulses beamed out by another craft trying to detect it? these impulses could then be passed on and sent out by speakers on the opposite side of the sub, and relayed along on their underwater path of travel.

thus the sonar waves would appear to be striking no obstacle—and no echo would return to the sonarscopes on the search craft!

"jumping jets!" tom thumped his fist on the workbench in his excitement. "i'll bet that's the answer, all right!" he grinned. "brand my boot heels, it's partly due to good old chow!"

he grabbed a pencil and began sketching his idea on paper. it would be necessary to spot the receivers and transmitters all over the hull of the submarine. diagrams and pages of scribbled computations followed the rough sketches.

an invisible sub—one that sonar pulses would seem to pass right through, as if nothing were there! "seems so simple now that i have the key!" tom said to himself elatedly.

hours ticked by while he analyzed the wave action mathematically, then worked out a typical hookup for one of his jetmarines in a set of precise schematic drawings.

finally the young inventor dropped his pencil, picked up the telephone, and dialed bud barclay.

"hop over here, fly boy," tom told his chum. "something hot on the griddle!"

bud arrived in a few moments. tom showed him the drawings and explained his plan for dodging underwater detection. he also related how chow's remarks about the radio music had sparked the idea.

his chum slapped him on the back. "good going, tom!"

"let's fly right over to fearing and see how it works on a jetmarine!" tom proposed enthusiastically.

bud grinned but made no move. he stood looking at tom, arms folded and feet wide apart.

"well, let's go, pal!" tom urged impatiently, puzzled by bud's lack of response.

"what about the square dance?"

tom stopped short, feeling like a punctured balloon. he stared in dismay at his smiling, dark-haired copilot. "good night! i forgot again!"

with a sigh, tom added, "you're right, of course. we sure can't let the girls down twice. but at least let's get together all the gear we'll need when we do go to fearing."

"i guess we'll have time for that," bud conceded with a sympathetic grin.

tom assembled a mass of electronic equipment and phoned various enterprises' departments for other items. bud helped to collect them, and the boys trucked the paraphernalia out to a hangar to be loaded aboard a whirling duck. then they scootered back to the lab for a quick shower and change.

twenty minutes later, in sport jackets, checked shirts, and slacks, the two chums hopped into bud's red convertible. they picked up sandy and phyl and drove a little way into the country for dinner at a huge old farmhouse restaurant.

"well, the evening's off to a good start," sandy said with a happy laugh as they headed back along the lakeshore road to the yacht club.

"hope i didn't put away too much fried chicken to sashay properly at the square dance," bud remarked.

tom chuckled. "don't worry, pal. you always untangle those feet of yours when the fiddle strikes up!"

the blazing lights of the yacht club were reflected in the blue-black mirror of the boat basin. bud parked and they went inside.

"welcome, buckaroos!" chow winkler greeted them with an enthusiastic bellow as they entered the dance room.

the old cowpoke was splendidly dressed in a maroon satin shirt and white whipcord breeches tucked into shiny new boots. but instead of his usual sombrero, a chef's cap was perched on his head.

"chow! you look marvelous!" sandy said.

the cook blushed with pleasure. "you gals look purty enough to charm a hoot owl right off'n his perch!" he shot back. both phyl and sandy were wearing gay calico dresses that had full swirling skirts.

the room was decked out with colored bunting and twisted crepe-paper streamers. and at one end of the dance room, chow had rigged up a model of a western chuck wagon.

"real atmosphere!" tom said admiringly. "chow, you've done us proud!"

"thanks, boss." the cook, who had asked especially to take charge of the decorations, glowed at the praise. then he became serious. "but what's keepin' that dad-blamed fiddler?"

the guests soon began to stream in, but half an hour went by, and lester morris and his fellow musicians had not arrived.

"i'd better phone his house," tom decided worriedly.

mrs. morris answered. she seemed surprised at tom's call. "why, my husband's playing at a party over in carterton this evening," she said. "are you sure you engaged him for tonight?"

"i'm positive," tom replied.

"just a moment, please. i'll look in his date book to see if there's been a mistake."

a minute later her voice came over the line again. "i'm terribly sorry, mr. swift, but your name isn't listed anywhere on lester's schedule."

the others saw from tom's face as he hung up that something was wrong.

"what gives?" bud asked anxiously.

"no music for one thing." tom reported what mrs. morris had told him.

"but you hired the guy!" bud protested. "and sandy and i talked to his agent!"

tom was already piecing together the mystery. he shook his head thoughtfully. "i'm sure now the whole deal was a hoax, bud," he declared. "both the first call that supposedly came from lester morris, and the second one asking me to come here and talk things over."

by not responding to the second call in person, tom went on, he had probably saved himself from being waylaid or kidnaped by his enemies.

"thank goodness!" sandy exclaimed. "still, that creepy len unger was trying to get information from us."

"but how did your enemy know about the dance, tom?" phyl newton put in.

sandy snapped her fingers. "i know! i'll bet it was when we went shopping for our dresses, phyl, right after the boys invited us! the department store was full of people—almost anyone might have heard us discussing the dance!"

"especially if he was already trailing you to pick up bits of useful information," tom agreed.

bud whipped out a handkerchief and mopped his face nervously. "the question is what do we do now, chums? a roomful of guests and no music!"

"relax, pardners!" chow broke in cheerfully. "just keep things goin' for a spell, an' i'll fix things up pronto!"

doffing his chef's cap, chow hustled out to his parked jeep and took off with a roar. mystified but hopeful, tom, bud, and phyl did their best to entertain the guests. sandy had rushed to the telephone. in twenty minutes chow came rushing back.

"hey! he has a fiddle!" bud exclaimed.

mounting the platform, the stout cowpoke raised his hands and shouted for attention.

"ladies an' gents, we'll start off with that good old dance known as the texas star!"

as everyone took his place, chow tuned up hastily. then he tucked the fiddle under his chin, stomped out the rhythm, and launched into a lively rendition of "turkey in the straw" while he called out the accompaniment:

"gals to the middle, then back so far!

gents step up for a clockwise star!

now shift hands and twirl t'other way,

we'll keep on dancin' till the break o' day...."

the dance number finally ended to thunderous applause. chow, puffing and red-faced but wreathed in smiles, was soon ready for another. half an hour later, a dance band of high school boys, hastily summoned by sandy, arrived to spell the texan.

the irrepressible chef, however, continued to call out most of the numbers and proved to be the hero of the evening. he gained even more acclaim for his delicious french fried potatoes and "steerburgers" served during the pause for refreshments.

"oh, chow! what would we ever do without you?" sandy said, and the cook beamed.

suddenly, in the midst of the lively chatter and laughter, the dance floor was plunged into total darkness!

phyl clung fearfully to her escort. "tom!" she gasped. "this is another trick of your enemy's to harm you!"