at the end of the test period, bud had prepared to bring the jetmarine to the surface. but just as he was about to blow the ballast tanks, mel flagler sang out a warning from the sonarscope.
"whoa! hold it, skipper! i think we have company on the starboard beam!"
bud jerked his head around in surprise. "you mean the sea hound?"
"no, she surfaced," mel reported. "can't make this out yet, but it could be another sub."
bud turned the controls over to zimby cox. then he rushed to the scope and examined the blip. "seems to be moving away from us on a westerly course. it's about two miles from here."
he donned the hydrophone earset and listened. "it's no seacopter, nor a jetmarine either," he announced presently.
"a navy sub, maybe?" suggested zimby.
bud shrugged. "let's find out." he ordered a change of course, hard to the right, and gunned the jets to bring the jetmarine directly on the mystery object's trail.
"it's a sub, all right," he said a short time later, listening again over the hydrophones.
"pretty close to fearing island, isn't it?" put in mel flagler. "that's a government-restricted area."
bud nodded grimly. "but staying just out of sonar range from the base."
the jetmarine closed steadily on its quarry. in a few minutes they were able to make it out dimly through the cabin window, dead ahead.
"that's sure no u.s. navy sub that i know of," bud said. "probably an enemy snooper."
"what if they spot us?" zimby asked.
bud chuckled. "that's the beauty of it, pal! don't forget. with this new antidetection gear we're invisible to them. at least as long as they don't run into us or we into them," he added.
"or unless they have superdetection equipment we don't know about," cautioned mel flagler.
as they talked, the unidentified submarine was bearing steadily toward the mainland. fathometer soundings showed it was on a steep upward slope of the continental shelf.
presently a foaming gush of bubbles showed that the sub ahead was blowing its tanks. the jetmarine followed as it surfaced and bud hastily manned the periscope.
"what're they up to?" mel asked tensely.
"don't know yet, but the hatch is opening," bud reported. suddenly he gave an excited gasp. "jumpin' jets! they're sending out a couple of frogmen!"
bud's companions were electrified by the news.
"spies!" zimby exclaimed.
"what do we do now?" piped up mack avery, the third man in bud's crew. "hadn't we better radio the coast guard and the fbi?"
bud wrenched away from the eyepiece. "i have another idea! any of you fellows game to go with me and capture those spies?"
all three of his companions volunteered eagerly. bud chose mel flagler, then took another sight through the periscope.
"the sub's submerging again," he reported. "that'll give us a clear field. zimby, you and mack keep an eye on that baby while we're gone, and be plenty careful she doesn't spot you!"
"roger! and take this roll of wire to tie up your prisoners."
hastily bud and mel changed into swimming trunks and donned hydrolungs. they went out through the air lock, plunged into the bracing salt water, and switched on their ion-drive units.
"can you see 'em?" mel asked over his mike.
"not yet. let's speed up before we lose 'em completely!"
both pushed their ion drives to capacity, scanning the water ahead in all directions.
"there they are!" bud exclaimed presently. he pointed to two tiny figures, barely visible in the distance.
"wow! they're sure not wasting any time!" mel muttered. "let's step on it, bud! they'll be ashore in a minute!"
a darting school of sea bass screened the figures briefly from view. as the fish flickered past, mel and bud saw the frogmen breast-stroke up toward the surface and break water.
bud and mel followed. ahead lay a barren stretch of beach, humped with sand dunes. it was skirted beyond by a thick fringe of trees.
"they certainly picked a perfect spot for a sneak landing!" bud thought. the beach seemed totally deserted, with no sign of human habitation.
by this time, the frogmen were scrambling ashore. within moments, bud and mel were on their heels. the raiders whirled in dismay as they caught the sound of footsteps rushing up behind them through the sand.
bud and mel hurled themselves forward, each dropping a man with a flying tackle. all four went down in a struggling, kicking tangle of arms and legs.
the battle was rough but short. bud and mel had the advantage of surprise, and soon pommeled and grappled their foes into submission.
bud, astride his opponent's chest with knees pinning the man's arms, unlooped from his belt the wire he had brought.
"here! take some of this and wire your man's wrists together!" bud told mel.
when the frogmen were safely bound, bud and mel allowed them to stand up. neither captive tried to escape.
"now, my sneaky friends, talk!" bud snapped. "what kind of a sightseeing trip did you plan?"
the frogmen's jaws remained tightly clamped. both looked flushed and sullen as they faced their captors.
"got their lips zipped, i guess," mel said disgustedly.
bud decided to try another tack. "doesn't matter," he said carelessly. "we know they're pals of the mirovs."
both men started as if they had been stung. bud followed up quickly, hoping to prod them into some unguarded remark.
"just as we thought!" he snarled. "a couple of low-down brungarian rebels! and up to their usual amateurish spy stunts!"
the raiders' eyes blazed, but they maintained silence. both, however, kept darting looks of keen interest at the americans' hydrolung gear.
just as bud was wondering how he could get the prisoners to the nearest police headquarters, a jeep came bouncing into view across the sand.
"hey! police!" mel exclaimed with a happy grin.
"we're in luck," bud said. "they can take these creeps off our hands."
the jeep braked to a halt a few yards away, and two uniformed officers hopped out.
"what's going on here?" said one, who was wearing a sergeant's stripes. the jeep had the words beach patrol stenciled on it in white paint.
"we just nailed these two brungarian frogmen," bud explained. "a sub put them ashore—probably as spies or saboteurs. they won't talk to us, but maybe you can pump them at headquarters."
the startled sergeant turned a cold eye on the two prisoners. "got anything to say for yourselves?" when neither answered, he unholstered his revolver and covered them. "better take off those wires and put bracelets on them, mike," he told his fellow officer.
the frogmen were handcuffed with cool efficiency and bundled into the jeep. meanwhile, the sergeant turned back to bud and mel.
"you fellows come along too," he ordered.
"but we haven't got time," bud protested. "our own sub's waiting right offshore and we want to tail the sub that brought those guys here! we're from the swift rocket base."
"any identification?" the sergeant asked.
"how could we have in this getup?" mel retorted.
"that's what i thought. so get moving," the sergeant barked.
reluctantly, bud and mel hopped onto the running board and clung to the bouncing jeep as it sped to the nearby town of sandbank. at headquarters they were questioned by the local police chief.
"if you'll call swift enterprises at shopton, sir, mr. swift—or harlan ames of the plant security department—will vouch for us," bud said.
the chief picked up the telephone and soon had mr. swift on the line. after speaking to him briefly, he passed the phone to bud so the scientist could identify his voice.
"that's bud barclay, all right. he's one of our most trusted employees," mr. swift told the chief after hearing bud's story.
the officer promised to release mel and bud at once. before doing so, however, he took them into the adjoining office where the two frogmen were being questioned.
"any luck?" the chief asked the sergeant.
sergeant gryce shook his head in disgust. "not much. they did admit they came in a sub, but they claim it didn't wait to pick them up."
the police chief shot a few questions of his own at the men, but they answered either in curt monosyllables or not at all.
"look, sir," bud put in, "if they're telling the truth about their sub not waiting, our jetmarine may have chased it. that means mel and i are stranded here. could you have your men wait for us on the beach till we find out?"
"gladly," the chief replied. "you two have done a fine day's work."
after the prisoners had been locked up to be handed over to the fbi, the two beach patrol officers drove bud and mel back to the area where they had landed. just as the jeep turned down the dirt road leading to the shore, bud's keen eyes spotted a lurking figure in the distance.
"stop, please!" bud said, tapping the driver on the shoulder.
as the jeep halted, bud pointed toward the beach. a man was crouching behind a sand dune, with a large fish basket beside him. the sergeant, puzzled, took out a pair of binoculars to study the situation. fortunately, the jeep was still screened by trees, and the crouching man evidently did not realize he had been seen.
"what's in the basket?" bud asked. "could it be clothes?"
"sure looks like it," the sergeant said, passing over the binoculars.
after a brief look, bud explained the hunch that had occurred to him. "i'll bet that guy's waiting with clothes for the frogmen. he probably got here late and doesn't realize they've been nabbed!"
"well, he'll soon find out," the police driver said grimly. he was about to start up the jeep when bud stopped him again.
"wait! you have no proof that's what he's here for," bud pointed out.
the pilot suggested that the police keep out of sight while he and mel approached the man in their swimming gear. "if that stranger takes the bait, we'll really have the goods on him!" bud concluded.
"smart idea, son," the sergeant said with a dry chuckle. "go to it!"
bud and mel circled widely through the trees, took a quick dip in the water, then approached along the beach as if they had just landed and were searching for someone.
to their delight, the man rose from behind the sand dune and hailed them. bud and mel hurried over to him.
"you have clothes for us?" bud asked. "we just came ashore from the sub!"
"yeah, right here," the man said in english with no trace of an accent. "thought i'd missed you."
"thanks, pal—that's all we want to know!"
the man gaped in comic dismay as bud pounced on him and pinned him to the ground. moments later, the two police officers rushed up and handcuffed him.
"hey! what's the big idea?" the man stammered. "i ain't done nothing. just got a phone call this morning, offering me fifty bucks to bring two sets of clothes down to the beach at five o'clock for a couple of divers."
"tell that to the fbi!" snapped the sergeant.
when the officers had departed with their new prisoner, bud and mel, both grinning, dived into the surf and headed out to sea.
in a few minutes they were sure they were at the right spot to meet the jetmarine. but it was gone!
