Over the jungle cove rolled an unbroken cloud of billowing, greenish smoke. It blotted out the white beach, spread out over the blue water, and crept slowly outward toward the anchored gunboat.

From its murky edge came the roar of powerful engines. The seaplane’s nose emerged from the poisonous smoke, slid swiftly over the waves, and rose like a great white gull into the clear upper air.

Aboard the gunboat, steam winches began weighing the two anchors, while officers and seamen hurried to batten down hatches and close ventilators. Slowly the craft’s sharp bow swung seaward. Her twin propellors churned white water at her stern.

Neither the launch nor its erstwhile occupants could be seen beneath that greenish cloud of poison gas. In vain the seaplane’s pilot circled the big airship over the jungle’s edge, looking for a break in the smoke.

“Fly lower, Panama!” commanded the hard-jawed man in the after cockpit. “If that stuff thins, even for a moment, we may be able to spot somebody. There’s eleven souls down there, at death’s door for all we know.”

“That’s where we’ll be, Mr. Splendor, if the gas hits us!” replied the pilot. “But here goes.... Look! The wind’s made a rift in the cloud! There’s the launch, and a couple of men sprawled beside it!”

“Drop landing gear!” cried Splendor, as the plane’s nose dipped earthward. “Land in the cove and taxi right up onto the beach. We must get those poor fellows to the gunboat or die trying!”

With a quick nod, Panama cut the throttle. An instant later the seaplane’s pontoons touched the water in a flash of white spray. Straight into the thinning gas cloud the ship plunged, heading for the level beach.

To anxious watchers aboard the gunboat, it looked as if Michael Splendor and his plucky pilot had committed deliberate suicide. Unable to see the rift which Panama had spotted from the air, they waited in agonized suspense for the plane’s reappearance.

Suddenly Captain Riggs raised a pointing arm.

“There’s the plane, now, but something’s wrong, Lieutenant!” he exclaimed, to the junior officer beside him. “See how low she rides in the water! And what under the sun are those dark blotches on the forward fuselage?”

Peering through his binoculars, Lieutenant Darnley cried out in amazement.

“They’re men, Captain!” he reported. “Mr. Splendor is holding two of them, and there’s another in his cockpit. All three look to be unconscious, sir!”

“Lower the whaleboat!” bellowed Riggs, leaning over the bridge’s rail. “Stand by to take men off the seaplane. Darnley, tell the medical officer to prepare berths in the sick bay. I’m going in the boat myself!”

Moments later the seaplane’s crew gave up their helpless passengers to the whaleboat. Michael Splendor, his eyes streaming with tears from the poison gas fumes, insisted on going back at once for another rescue attempt.

“We’ve still to find the main shore party, Captain!” he explained between gasps for breath. “There’s young Winslow and Pennington still to be found, not to forget Admiral Colby’s daughter. Every second will count if we’re to save their lives!”

“You’re right, Mr. Splendor!” agreed Riggs, balancing in the whaleboat’s sternsheets. “We’ll follow you inshore, as soon as we get these poor fellows aboard. The smoke looks to be thinning now. Good luck!”

His words were drowned out by the roar of the seaplane’s motors. Like a huge water bird she taxied around, heading back to the beach. At the same moment, the boat’s oarsmen gave way with short powerful strokes that sped them toward the waiting ship.

Once alongside, the boat falls were made fast by expert hands, and the whaleboat was lifted dripping from the water. Even before the gassed seamen were transferred to the sick bay, the ship was nosing shoreward to join in the next desperate attempt at rescuing Don Winslow and his gallant companions.

Many hours later a westering sun cast its mellow rays through the portholes of the gunboat Gatoon, now a floating hospital anchored off the coast of Haiti. In the vessel’s sick bay, a white-coated medical officer bent frowning over one of the ten occupied berths. So intently was he watching the patient that he failed to hear the door open, or see the approach of the big man in the wheelchair.

“I thought this is where I’d find you, Doctor!” exclaimed the latter, his tone warm with a touch of Irish brogue. “They told me the seaman, Jerry, is sinking fast!”

The young doctor turned with a shake of his head.

“He’s in pretty bad shape, Mr. Splendor,” he said wearily. “The others are coming around surprisingly well, though. Even the girl, Miss Colby. I expect Commander Winslow and Lieutenant Pennington will regain consciousness this evening.”

“That’s just fine, Doctor!” exclaimed Splendor heartily. “Do ye mind if I go along when next ye look in on ’em. Even with me crippled legs, I promise not to be in the way.”

“Come along, of course, Mr. Splendor,” smiled the medical officer, opening the door. “If you and your seaplane had been OUT of the way this morning, none of these men would be alive now. You’re pretty much of a hero on this ship, whether you know it or not!”

“You mean my pilot, Panama!” growled the big man, rolling his chair along the steel deck. “It was him who did the rescuing, while I sat helpless in me cockpit.... Ah! So this is the cabin where ye put Don Winslow and his redheaded mate, eh?”

With a nod, the doctor threw open the cabin door.

“They seem to be still asleep, both of them,” he murmured, glancing across the narrow room. “Here! I’ll help you with that chair, if you’d like to come in.”

Low pitched as they were, the words registered on Don Winslow’s slumbering senses. He stirred, opened his eyes, and struggled up on one elbow.

“Michael Splendor!” he exclaimed huskily. “I dreamed about you, and a seaplane, and a cloud of poison smoke and.... Say! Where are we, anyhow? And what am I doing in this cabin?”

Rolling his chair swiftly to the side of the berth, Michael Splendor held up a big hand.

“Whisht, and be quiet, young feller-me-lad!” he rumbled. “It was no dream ye had about the poison smoke. Ye’re still sick from it, so take it easy. Your mate, the redheaded lieutenant, is sleepin’ in the next berth to ye.”

“I am not, Don!” croaked Red Pennington, trying to sit up. “I was lying low so as not to wake you! Oh-h-h! Golly! Does my head hurt!”

“It will be worse if you don’t lie down, Pennington!” snapped the medical officer. “If you and Commander Winslow didn’t have leather lungs and cast iron constitutions, we’d be sewing you up in canvas right now, for a sea burial. You two got the biggest dose of smoke!”

“But Mercedes—I mean, Miss Colby—she must have been gassed too!” cried Don Winslow, from the other berth. “Is she coming out of it yet, Doctor? Tell me the truth....”

“Hush, lad!” soothed Splendor, pushing the young officer back onto his pillow. “Miss Colby’s out of danger, so don’t excite yourself. We got Yanos and the two fishermen in time, too, along with the launch’s crew. Ye’ll hear all the details tomorrow, when you’re feelin’ stronger. The doctor and I will be leavin’ ye now.”

“But—the underground base!” muttered Don weakly, pressing a hand to his aching eyes. “About that apparatus, and the automatic weather map—Tell me, Splendor....”

“We’ll talk about that another time,” said the man in the wheel chair. “There’s nothing to worry about, except the strength ye’re wastin’ this minute, Commander. So pipe down and give your thoughts a rest till ye’re called on deck. The same goes for you, Pennington, d’ye hear?”

“Aye-aye, sir!” came the redhead’s mumbled response, as the cabin door closed softly behind the visitors.