"the space people or some enemy's invadin' us!" chow shouted. "take a squint through your telescope, boss! brand my bazooka, they may be landin' any second!"

more people came streaming in, attracted by the chef's cries and gesticulations. some were bewildered, a few frightened. others were laughing, thinking the whole thing a joke. the scene was rapidly taking on the proportions of a riot!

"whoa! slow down, chow!" tom ordered, trying to make himself heard above the din.

"it—it's the truth, boss!" chow stammered, mopping his brow with a huge red bandanna. "why, sufferin' rattlesnakes, didn't i hear 'em spoutin' their space lingo with my own ears?"

"you heard what?" bud said.

"spoutin' space talk!" the cook repeated. "it come right over the loud-speaker in the galley! they was chitter-chatterin' plottin' to blow us all to smithereens!"

"that's a fact! we heard it, too!" one of the workmen chimed in.

tom and bud looked at each other blankly. then suddenly tom's eyes kindled with a dawning suspicion. whirling around, he rushed over to inspect the public-address outlet on the wall.

meanwhile, mr. swift had just driven in through the main gate of enterprises. "what's going on?" he asked the guard at the gate, noting the excited hubbub around tom's laboratory.

"don't rightly know, sir," the guard replied. "i was wondering myself. i know it sounds crazy, but i thought i heard someone yelling there was going to be a space attack."

mr. swift's eyebrows lifted in amazement. without further discussion, he stepped on the accelerator and sped off along the paved drive. seconds later, his car braked to a stop near tom jr.'s private laboratory. the scientist jumped out and made his way through the milling crowd.

"what's going on?" mr. swift stared in astonishment at tom and bud, who were both doubled up with laughter.

"a scrambled radio alert, dad," tom gasped between chuckles. "chow thought some martian monsters were invading us, and sort of pushed the panic button."

the texan blushed as tom explained what had happened. realizing chow's embarrassment, tom tried to make his mistake sound understandable.

apparently the power line to the ion-drive control board had somehow picked up the boys' scrambled conversation underwater. the signal had been transferred by inductance in the wall wiring and amplified over the public-address system.

"our wall mike was on," tom added, "and it probably picked up some of the sound waves from the tank. anyhow," he concluded, slapping the cook affectionately on the back, "i'm sure glad we have a wide-awake hombre like chow in the outfit. it wouldn't be the first time he's saved our necks!"

chow perked up, and the employees, reassured, returned to their jobs.

"i have some news of my own," mr. swift announced with a smile as the room cleared. "but i'm afraid it'll sound pretty tame compared to a space attack."

"let's hear it, dad," tom said eagerly.

"i've been conducting some experiments with those space plants," the elder scientist said. "it looks as though they may prove to be a valuable nutritional source."

the plants, mr. swift went on, showed promise of producing enormous amounts of protein quickly and cheaply—enough to increase the world's food supply by a sizable margin. moreover, he had isolated a vitamin in this protein not found in any of man's present foods.

"doc simpson has been working with me," mr. swift concluded. "he has been doing some experiments of his own with a vitamin extract from the space plants. he thinks it may prove highly beneficial to human beings."

tom was thrilled, and even bud realized that mr. swift's cautious report could well turn out to be of history-making importance.

"i'd say your news makes a phony space attack look pretty tame, dad," tom said, his eyes flashing enthusiastically. "with the earth's population increasing, this could be the answer to the food problem."

"don't tell chow," bud added, "or we may find spaceburgers on the next menu!"

the swifts chuckled. chow's hobby of concocting weird dishes was a standing joke at enterprises, and already had led to such dubious triumphs as armadillo stew and rattlesnake soup.

monday morning tom buckled down seriously to the job of designing an undetectable sub. his drawing board was littered with sketches and diagrams when the phone rang, breaking in on his thoughts. tom answered it with a scowl of impatience. the caller was lester morris.

"could you meet me at the yacht club to talk over the dance program?" morris asked.

tom hesitated. for sandy's and phyl's sakes he was eager to do everything possible to make the square dance a success. but on the other hand....

"i'm pretty busy today," tom said. "but my sister and my friend bud barclay can tell you what we want—probably better than i can. suppose i ask them to meet you there after lunch?"

there was a slight pause. "very well," morris agreed, although he sounded a bit annoyed.

after hanging up, tom phoned bud and asked him to keep the appointment. bud was only too happy to oblige, jumping at the chance to take sandy out to lunch beforehand.

at one o'clock the husky young pilot and his date strolled into the yacht club lounge. lester morris was nowhere in sight, so they sat down to wait. twenty minutes later the musician still had not appeared.

"i hope he hasn't forgotten," sandy said, glancing at her wrist watch.

"if he's a square-dance caller, his memory ought to be extra good," bud joked. "fine thing if he can't even remember the time of day!"

after waiting a while longer, bud decided to telephone morris's home. but at that moment a thin, seedy-looking man came into the lounge. his close-set eyes and loudly striped suit combined to give him a somewhat disreputable appearance.

"good grief! len unger!" sandy whispered. "what does he want with us?"

unger was walking straight toward them. both bud and sandy had met him occasionally around town and found him obnoxious.

"sorry, but morris got tied up," unger informed them. "he sent me to talk to you."

sandy's blue eyes met bud's in a flicker of distaste, but she tried to conceal her feelings. "please sit down," she invited unger politely. "what square-dance numbers does mr. morris do?"

len unger shrugged. "you name 'em."

"but, my goodness," sandy said, puzzled, "how do we know he'll have the squares i name?"

unger stared at her as if he did not quite understand. "you mean, can he call off the dances you want? if he can't, i'll let you know."

"does he do patter calls or singing calls?" bud put in.

again unger hesitated, then said, "both."

"wonderful!" sandy exclaimed gleefully. "i thought he only did singing calls." after a moment's thought, she went on, "well, let's see. what about 'birdie in the cage'?... and 'the gal from arkansas' ... 'uptown and downtown'...."

unger jotted the names on the back of an envelope. pausing a moment, he remarked, "guess your brother was too busy to make it today, eh, miss swift? what kind of ex-spearmints is he working on now?"

"i really couldn't say," sandy replied coldly. she always made it a point not to discuss tom jr.'s or her father's research work with outsiders.

unger persisted chattily, "i read where he handled that jupiter probe shoot for the navy."

"let's get back to square dancing," snapped bud. as he and sandy finished planning the program, len unger continued to drop remarks and questions about "the great tom swift" and his inventions. all prying queries were side-stepped.

as soon as possible sandy and bud cut short the conversation and left the yacht club. unger's face wore an angry sneer as they walked out.

"what a creep!" bud said, when he and sandy were driving back in his red convertible.

meanwhile, in his private laboratory at enterprises, tom was somewhat discouraged. he had tried several different experimental attacks on the problem of an undetectable submarine. none had worked out successfully.

"i thought that idea of a sonar-wave baffle might lead somewhere," he murmured, "but it looks as though i'm wrong."

flopping down on a stool at his workbench, tom cupped his chin in his hands. he was frowning, deep in thought, as the pudgy figure of chow winkler came into the laboratory.

"'smatter, boss?" the cook inquired cheerfully. "ain't your ole think box workin' today?"

"doesn't seem to be," tom confessed.

"give it time, son. tomorrow's another day," chow said philosophically. "what you need is a haircut for the square dance."

tom laughed in spite of himself. "maybe you're right, chow. might help me think better."

tom got off the stool and stretched out the kinks in his legs. he strolled outside with chow, then scootered to the parking lot and hopped into his sleek, silver sports car.

a moment later he was whizzing off in the direction of shopton. nearing town, tom turned off on a side-road short cut. he noticed in his mirror that a truck behind him also turned off.

"really barreling along!" tom thought. "if you're in such a hurry, the road's yours, pal."

he pulled over sharply, motioning the truck to pass. instead, to tom's surprise, it closed in straight behind him. the next moment, tom saw a port open below the truck's hood and a strange-looking device pop out on a springlike steel cable.

it clamped magnetically to tom's rear bumper! his car was caught like a fish on a line!

tom stepped on the accelerator, trying to pull free. the truck at once swerved off the road, steering around a utility pole. as the cable tautened, there was a sickening screech of metal and the sports car was brought to a crashing halt!

tom's head slammed against the side window. with a groan, the young inventor blacked out.