“Supersonic sound, that is sound waves that are too high-pitched for the human ear to hear, but these sounds were not meant for the human ear as you can see.”

Two men appeared, the first of them leading a small dog on a leash. Tracy bent to pet the beast and explained. “Trained to come to that sound. These are my men who have been keeping watch over us waiting for my signal.”

“I had no idea they were there.”

“They are professionals.”

Tracy issued swift orders, then he and Gus went forward once again. “My operators will surround the area and close in, but I must lead the attack. You need not come with me—”

“I am your man.”

“Good. I was hoping you would. I want you there when the curtain falls on the last act of this little drama.”

Tracy went first, silent as a cat, with Gus a few yards behind. They stayed close to the walls, in the darkness, and worked their way to the spot nearest the ship, where a single tiny lamp on deck cast a weak glow on the battered gangway. Tracy halted for a moment, looking at the ship, and when he did a shadow detached itself from the wall behind him and lurched forward.

Gus had only a split second to act in, and he did not want to call out a warning, so he jumped forward as well. His fist came up in a short, wicked arc that ended on the mysterious assailant’s jaw with a sharp crack that caused Tracy to spin about. There was a small thud as the club the man had been wielding fell to the cobbles, then Tracy was helping Gus lower the unconscious man to the ground as well.

“I am glad you are here, Washington,” said he, and from a man of his professional caliber this was reward enough. “That was a blow well struck and my men will have him before he regains consciousness. They will be closing in now to cut off all means of escape by the criminals, while fast launches will prevent flight by sea. The final act of this drama is about to be played. You were correct in your deductions, for I have checked my direction finder. Billygoat is aboard that ship. Now here we go.”

Silent as a wraith he drifted forward, with Gus a few paces behind. They passed under the counter of the ship and her name could now be seen, picked out in rusty letters across the stern. Der Liebestodt, Lucerne. Swiss registry, a flag of convenience obviously, with the real names and nationality of the true owners well concealed. But not much longer. All was silent on the deck above, the ship darkened except for that single bulb at the entranceway. Tracy walked forward steadily as though he belonged here and mounted the gangway, with Gus not too far behind. Yet, quiet as he was, he was not unobserved, for when he reached the deck a man stepped out of the shadows and mumbled something inaudible to Gus who was still on his way up. Tracy answered and pointed down and, as soon as the man had turned, the operative’s hands struck and did something to the other’s neck that kept him rigid for long moments before he folded and fell to the deck.

There was still no alarm, and Gus could not believe it. They had boarded the ship, rendered two men unconscious, and their presence was still unknown. Their luck seemed too good to last and he hoped that would not prove the case. Tracy waited in the open doorway until he came up, then whispered into his ear.

“The deckhouse is quiet and there is no one on the bridge—so the miscreants must be below. Follow me as silently as you are able.”

With these words he pushed open the heavy iron door to disclose a dimly lit passageway beyond, into which he drifted. The first door off the passage was dark and he passed this opening with only a quick look, and the next, dark and open as well. But the one that followed was closed and he bent to peer through the keyhole, then took a doctor’s stethoscope from his pocket and listened at the door panel with it. Satisfied, he restored it to his pocket and waved Gus on, pointing to the stairwell at the same time. Down this they went, slowly and carefully, and their reward was immediate for one of the doors on this deck stood partly open and from it emerged a bar of light and a mutter of voices. Still leading, Tracy went forward, past another darkened doorway, with Gus close behind. As Gus passed the same doorway a dark figure, knife clutched in hand, leaped to the attack.

Only split-second reflexes saved his life. Gus fell back as the man hit him, falling under the swooping slice of the weapon, clutching at the knife arm, and rolling away with his assailant on top of him. There was a hearty thud as they fetched up against the bulkhead opposite, the force of the impact stunning the man for an instant, the force of Gus’s fist stunning him more lastingly so that he sighed and went limp and the knife fell from his hand and rang loudly on the metal deck.

In the silence that followed the voice could be clearly heard through the open door.

“What was that? I heard something in the passageway.”

Tracy stayed himself no longer. His revolver appeared in his hand and, as he kicked the door wide, he shouted defiantly, “This is the law and you are all under arrest!” then sprang into the room.

There were shouts, shots, muffled screams as Gus plunged forward, hurling himself without hesitation into the unknown fray, into a large cabin seemingly filled with rushing men. One of them tried to escape but Gus was in his path and a hard fist in his middle bent him double, lowering his chin to the correct spot to connect with the other fist on its way up. Gus plunged on into the melee and raised his arm to prevent a blade from descending that was slashing at his throat and a red arrow of pain shot through his biceps as the blade cut deep. But he still had a good arm that ended in an equally good fist that dropped the attacker on the spot.

With that the battle was over although Gus did not know it as he struggled to his feet, ignoring the pain of his wound. Disreputable men damaged in various ways lay sprawled about the room while Billygoat sat astride the single conscious survivor banging his head against the deck so that he could join his comrades in unconsciousness. Tracy moved quickly about putting handcuffs on any that showed signs of life while Billygoat ceased his banging and rose, dusting off his hands and pointing at a closed door on the far side of the cabin.

“He went through there during the fracas. The Gray Man, the one in charge.”

Tracy took in the situation in an instant and kicked a wicked looking automatic pistol across to Billygoat who swooped it up.

“Guard the prisoners then because I want as many as possible alive.”

Even as he spoke he was hurtling across the room to smash his shoulder into the flimsy connecting door, bursting through it with Gus, who had tied his kerchief about his wounded arm, right behind, straightening up and raising his gun and saying, “You will stop right there for the jig is up.”

The man he had addressed did stop what he was doing and straighten up slowly with a sheaf of papers in his hand. He had been thrusting these along with others of their kind into a metal wastebasket within which a smoky fire flared. As soon as Gus was aware of this he leaped past the Pinkerton man and kicked the basket over to stomp out the smoldering flames. Only when this task was done did he straighten up and look at the man they had captured, the secret protagonist at last.

He was indeed a gray man as Billygoat had said. He stood erect beside the desk there, one fist pressed to it, the other to his chest, swaying slightly. From toe to top he was gray, clad completely in gray from the gray spats that covered his gray shoes, gray top coat and gray suit, of a good cut, gray broadcloth shirt with matching gray tie, a gray fedora upon his head and a mask of gray cloth that concealed his face except for the pair of holes cut in the fabric through which peered a pair of gray eyes.