Don Winslow’s brief account of the two attacks on Red and himself did little to clear up the mystery which hung like a dark cloud over the Gatoon’s after guard. Both assaults appeared to have the same object, however—to get back the stolen enlistment records which Don had found hidden in the lifeboat. For some reason the enemy was afraid to have those records examined.

“That’s how I’ve figured it out,” Don told the little company gathered in the captain’s cabin, “either the records of Scorpion agents among the crew are missing, or they’ve been forged. In any case, a careful check should tell the story.”

Spreading out the rumpled enlistment papers on the captain’s table, he commenced a swift search, while Riggs and Red Pennington looked over his shoulders. All at once he picked up one of the documents and smoothed it out. The name on the outside read: “Anton Corba,” with the rating noted as “Radioman, First Class.”

“But why pick that one, Commander?” asked Captain Riggs sharply. “What reason have you to suspect....”

“Look, Captain!” Don Winslow interrupted. “The signatures on this record show signs of tracing. Forgery, all right, but a mighty clumsy job. Just study it for a minute and give me your opinion.”

Handing the paper to Riggs, he whispered rapidly in the officer’s ear:

“I have a hunch we are being overheard now. Corba or some other spy may be the eavesdropper. I’m sending Pennington out to check up. Meantime we must all keep talking naturally, so the fellow will not suspect.”

With a nod of understanding, Riggs moved over to Michael Splendor’s chair.

“I see what you mean, Commander,” he said loudly. “At least one of these signatures looks smeary, but I’m no handwriting expert. Tell me what you think of it, Mr. Splendor. As chief of the Haitian Naval Intelligence, you should know about such things.”

Stooping quickly, he whispered Don Winslow’s plan to the cripple. At the same instant Don was muttering advice in Red’s ear.

“Take off your shoes,” he told the wide-eyed lieutenant. “Sneak up topside and try to locate anyone who may be eavesdropping. If you don’t spot anyone, come back in five minutes. Here’s my flashlight. Shove off now, and good luck! We’ll carry on the show down here till you report or signal us.”

As Red silently closed the cabin door behind him, he heard Michael Splendor’s voice within, taking up the mock discussion. The “show” as Don called it, would be quite convincing to any eavesdropper.

And if Don was right in his guess, the spy should be easy to surprise at his work. At that hour of night, no enlisted man would have any legitimate business hanging around the cabin ventilators.

Silent as a shadow, for all his bulk, Red Pennington emerged onto the starlit deck. Slipping aft, he rounded the cabin skylight and probed the shadows under the port rail.

No glimpse of a furtive lurker rewarded him, however. With a grunt of disappointment, he padded forward, heading for the midship’s superstructure.

“I’ll just take a look inside the radio shack,” he muttered under his breath. “Don seems to think that guy Corba’s enlistment was forged—which means he may be the guy who shot at us, too. He’s got a fishy mug, anyway, and his story was a little too slick when we jumped him a few minutes ago!”

The door of the radio shack was on the port side. Therefore, as an extra precaution, Red circled the superstructure to starboard, halting at the corner of the galley.

The space between the deck house and the rail was empty, yet something about it looked queer. For a moment Red stood blinking in puzzlement, trying to make out what was wrong. All at once it came to him.

The radio shack door was open at least two inches; yet no light shone through onto the white deck.

Since Navy men do not go about leaving doors ajar, this suggested one of two things: either Corba had left in a desperate hurry, or he was still inside, with the lights out! Red Pennington intended to find out which.

With the utmost caution, he crept past the galley, noting that the door beyond him did not sway with the gentle roll of the ship. That meant it was propped open deliberately. But why?

Just as his hand was reaching for the knob, the door swung shut. Red froze in his tracks, his mind racing. Whoever had closed that two-inch opening could not have seen him. The door itself had hid his approach. The thing proved simply that the radio shack was occupied.

Before Red could plan his next move, a faint, metallic ticking caught his ear. Pressing his ear close to the shack’s steel wall, he made out the familiar chatter of a wireless key, sending in International Morse Code.

“—REPORTING—EMERGENCY—ABOARD—GATOON” Red silently spelled out the message. “AGENT SC-21 SEIZED. WINSLOW AND PENNINGTON HAVE DISCOVERED FORGED ENLISTMENT PAPERS IN LIFEBOAT WE PREPARED FOR OUR GETAWAY. THIS WILL LEAD ANY MOMENT TO MY ARREST AND THAT OF AGENT SC-17. PLEASE ADVISE NEXT MOVE. SC-3.”

While listening, Red Pennington had slipped Don’s flashlight from his pocket. As the message ended, he wrenched open the door and shot the bright beam into the radio shack. It’s spotlight steadied on the tense figure of Corba, seated beside the room’s small tool bench.

“Just hold that pose, sailor!” gritted the stocky lieutenant. “No—keep your left hand under the bench! Don’t move a muscle——”

Whipping out his pocket gun, Red slammed two shots at the steel decking, close to Corba’s feet. Instantly the white-faced radioman froze in his chair, his pose still as a statue’s.

“That’s better!” clipped the lieutenant, as shouts and the stamp of feet sounded from the cabin country. “In just a moment you’re going to tell your story over again; and it had better be the right one this time. Do you get me, Agent SC-3?”

Warned by Red’s sharp call, Don Winslow halted the captain and Lieutenant Darnley outside the radio shack. Stepping inside alone, he snapped on the lights.

“Great work, Red!” he approved, when the red-haired lieutenant briefly outlined what had happened. “We’ve caught our eavesdropper this time, and....”

He broke off as a harsh whisper rose, seemingly from beneath the workbench.

“AGENT SC-3 AND SC-17, ATTENTION!” the weird voice rasped. “YOU ARE INSTRUCTED TO LEAVE THE SHIP AT ONCE, USING LIFEBELTS. SEAPLANE WILL PICK YOU UP AT DAWN. SC-21 WILL PAY PENALTY FOR HIS FAILURE WHEN WE BOMB GATOON FROM THE AIR. THAT IS ALL!”

A gasp from the unhappy Corba gave Don Winslow the cue for his next play. Ignoring the startled questions of Captain Riggs and Lieutenant Allen, he faced the radio operator.

“All right, Corba!” he said tightly. “That message shows you just where you get off. Like SC-21, you’re going to pay the penalty for failure, when and if bombs start dropping on this vessel! Is your loyalty to Scorpia strong enough to stand up under that?”

Hollow-eyed with fear, the Scorpion spy shook his head.

“You’ve named it, Commander!” he said hoarsely. “The Scorpion don’t have much mercy for them that are fools enough to get caught. But what good’ll it do, sir, if I tell you what I know? We’re all bound for Davy Jones’ locker, now!”

Don Winslow’s laugh rang as hard as the slap of bullets on steel armor plate.

“We were, maybe, but we’re taking a new tack, sailor!” he barked. “Now we know what your murderous pals are up to, we can outthink and outfight them too. The only man aboard who’s bound for Davy Jones is——”

“Captain!” cried a breathless voice on deck. “The prisoner, Durkin—the man you put in the brig, sir—he’s dead! Hanged himself, with a loop of wire he’d made fast to a steampipe. We found this note, written on an old envelope. Here it is, sir!”

After a startled pause, Captain Riggs stepped inside to hold a crumpled envelope under the light.

“What do you make of this, Commander?” he growled. “Things are happening a bit too fast for me to keep my bearings tonight, this note, for instance! It says: 'I queered your engines and killed the Chief Machinist’s Mate. When the Scorpion strikes, you’ll think I did Ahern a favor. Signed, Durkin.’”

“And so exit Scorpion Agent SC-21!” observed Don Winslow harshly. “He killed himself rather than go down later with the ship. That leaves one enemy agent still unidentified. Who is he, Corba?”

“Seaman Second Class, by the name of Mink,” replied the radioman sullenly. “He’s just a tough gorilla we brought aboard for strong arm work. As it turned out, we didn’t have to use him.”

“Which means you were the bird who shot at us tonight from the corner of the galley!” put in Red Pennington. “You sure hated to let us get a look at those forged enlistment records, didn’t you, Mr. A. Corba?”

With a snort of anger, Captain Riggs turned to the door.

“The whole business smells like plain mutiny to me!” he declared. “While you’re questioning this man, Commander, I’m going to hunt up Seaman Second Class Mink, and throw him in irons! Join me in my quarters, gentlemen, when you’re ready to compare notes.”