"You said it! To be exact, the whole region is unexplored!"

"Unexplored!"

"Oh, the district is filled with mountains on most maps," Johnny explained. "But on the really accurate charts the truth comes out. There's a considerable stretch of country no white men have penetrated. And Doc's strange heritage is located slap-dab in the middle of it!"

"So we gotta play Columbus!" Monk snorted.

"You'll think Columbus's trip across the briny was a pipe when you see this Hidalgo country!" Johnny informed him. "That region is unexplored for only one reason — white men can't get into it!"

Doc had been standing by during the exchange of words. But now his calm, powerful voice commanded quick attention.

"Is there any reason we can't be on our way?" he asked dryly.

They took off at once in the monster, low-wing speed plane. But before their departure, Doc telephoned long distance to Miami, Florida, where he got in touch with an airplane-supplies concern. He ordered pontoons for his plane, after determining the company kept them in stock.

The approximately nine-hundred-mile flight to Miami they made in something more than five hours, thanks to the tremendous cruising speed of Doc's superplane.

Working swiftly, with lifting cranes and tools and mechanics supplied by the plane-parts concern, they installed the pontoons before darkness flung its pall over the lower end of Florida.

Doc taxied the low-wing speed ship out over Biscayne Bay a short distance, making sure the pontoons were seaworthy. Back at the seaplane base he took on fuel and oil from a seagoing filling station built on a barge.

To Cuba was not quite another three hundred miles. They were circling over Havana before the night was many hours old. Another landing for fuel, and off again.

Doc flew. He was tireless. Renny, huge and elephantine, but without equal when it came to angles and maps and navigation, checked their course periodically. Between times he slept.

Long Tom, Johnny, Monk, and Ham were sleeping as soundly among the boxed supplies as they would have in sumptuous hotel beds. A faint grin was on every slumbering face. This was the sort of thing they considered real living. Action! Adventure!

Across the Caribbean to Belize, their destination on the Central American mainland, was somewhat over five hundred miles. It was an all-water hop.

To avoid a head wind for a while, Doc flew quite near the sea, low enough that at times he sighted barracudas and sharks. There was an island or two, flat, white beaches bared to the lambent glory of a tropical moon that was like a huge disk of rich platinum.

So stunningly beautiful was the southern sea that he awoke the others to observe the play of phosphorescent fire and the manner in which the waves creamed in the moonlight, or were blown into faintly jeweled spindrift.

They thundered across Ambergris Cay at a thousand feet, and in no time at all were swinging wide over the flat, narrow streets of Belize.

The sun was up, blazing with a wild revelry. Away inland, the jungle was lost in a horizon infinitely blue.

Doc slanted the big plane down and patted the pontoons against the small waves. Spray fanned up and roared against the idling propellers. He taxied in toward the mud beach.

Renny stretched, yawned. The yawn gave his extremely puritanical face a ludicrous aspect.

"I believe that in the old pirate days they actually built a foundation for part of this town out of rum bottles," Renny offered. "Ain't that right, Johnny?"

"I believe so," Johnny corroborated from his wealth of historical lore. Plink!

The sound was exactly like a boy shooting at a tin can with a small air rifle.

Plink! It came again.

Then — bur-r-r-rip! One long roar!

"Well, for — " Monk swallowed the rest and sat down heavily as Doc slammed the engine throttles wide open.

Engines thundering, props scooping up water and turning it into a great funnel of mist behind the tail, the plane lunged ahead — straight for the mud beach.

"What happened?" demanded Ham.

"Machine gun putting bullets through our floats!" Doc said in a low voice. "Watch the shore! See if you can get a glimpse of whoever it was!"

"For the love of mud!" muttered Monk. "Ain't we never gonna get that red-fingered guy out of our hair?"

"No doubt he radioed ahead to some one he knows here!" Doc offered.

Distinctly audible over the bawl of the motors came two more metallic plinks. then a series. The unseen marksman was doing his best to perforate the pontoons and sink the craft.

All five of Doc's men were staring through the cabin windows, seeking trace of the one who was shooting.

Abruptly bullets began to whiz through the plane fuselage itself. Renny clapped a hand to his monster left arm. But the wound was no more than a shallow scrape. Another blob of lead wrought minor havoc in the box that held Long Tom's electrical equipment.

It was Doc who saw the sniper ahead of all the others, thanks to an eye of matchless keenness.

"Over behind that fallen palm!" he said.

Then the rest perceived. The sharpshooter's weapon projected over the bole of a fallen royal palm that was like a pillar of dull silver.

Rifles leaped magically into the hands of Doc's five men. A whistling salvo of lead pelted the palm log, preventing the sniper from releasing further shots.

The plane dug its pontoons into the mud beach at this point. It was not a moment too soon, either. They were filling rapidly with water, for some of the bullets, striking slantwise, had opened sizable rips. Indeed, the floats were hopelessly ruined!

Swiftly, grim with purpose, three men bounded out of the plane. They were Doc, Renny, and Monk. The other three, Johnny, Long Tom, and Ham, all excellent marksmen, continued to put a barrage of rifle lead against the palm log.

The log lay on a finger of land which reached out toward a very small cay, or island. Between cay and the land finger stretched about fifty yards of water.

The sniper tried to reach the mainland, only to shriek and drop flat as a bullet from the plane creased him. Meantime Doc, Renny, and Monk had floundered to solid ground and doubled down in the scrawny tropical growth. The smell of the beach was strong in their nostrils — sea water, wet logs, soft-shell crabs, fish, kelp, and decaying vegetation making a conglomerate odor.

To the right of the friends lay Belize, with scraggly, narrow streets and romantic houses with protruding balconies, brightly painted doorways, and every window as becrossed with iron bars as if it were a jail.

The sniper knew they were coming upon him. He tried again to escape. But he had not reckoned with the kind of shooting that was coming from the plane. He couldn't make it to the mainland.

Desperately, the fellow worked out toward the end of the land finger. Stunted mangroves offered puny shelter there. The man shrieked again as he was creased.

In his circle of acquaintances, it must have been customary to shoot prisoners — give no quarter — because he didn't offer to surrender. Evidently he was out of ammunition.

Wild with terror, he leaped up and plunged into the water. He was going to try to swim to the little island.

"Sharks!" grunted Renny. "These waters are full of the things!"

But Doc Savage was already a dozen yards ahead, leaping out on the land finger.

The sniper was a squat, dark-skinned fellow — but his features did not resemble those of the Mayan who had committed suicide in New York. He was a low specimen of the Central American half-breed.

He was not a good swimmer, either. He splashed a great deal. Suddenly he let out a piercing squawl of terror. He had seen a dark, sinister triangle of fin sizzling through the water toward him. He tried to turn and come back. But so frightened was he that he hardly moved for all his slamming of the water with his arms.