“So there you are, Inspector. That’s what the Bender sound detector discovered. Human ingenuity could do no more.”

Inspector Burton with difficulty repressed a smile at the inventor’s childlike vanity. Mr. Temple experienced similar difficulty. Ensign Warwick grew red in the face, and the boys made occasion to bow their heads. In reality, however, nobody need have attempted to hide his feelings, for the inventor was so constituted that he paid his auditors no attention. He was like many geniuses—a supreme egotist.

Those mentioned were seated in Mr. Temple’s suite. Doctor Marley alone of the party was not present, having been left aboard the Sub Chaser.

The inventor had spent a considerable space of time relating what had been learned through the medium of the sound detector. From San Francisco he had gone directly to Ventura and, after placing a sound detector in the government radio station at that point, had turned back to the station on top of the Santa Ynez mountain range behind Santa Barbara. For two days he had been listening vainly in the attempt to catch code messages which might be interpreted as coming from the secret radio station of the smugglers.

Success had come that morning, just after the storm. The heavy fog at sea had not reached to the mountains. It had been sunshiny and bright, and he had taken his listening post at an early hour.

Then, as he tuned his sound detector to varying wave lengths, had come a message in code—a code unlike any of the commercial codes registered with the government and of which he had obtained copies at San Francisco through the offices of Inspector Burton.

He listened. A conversation was being carried on between a ship at sea and a fixed land station. The ship, he now realized must have been the trawler; the station, the secret radio of the smugglers.

It seemed to him the sound detector located the fixed land station south-southeast of Santa Barbara, which would place it somewhere in the group of Channel Islands. This coincided with a bearing communicated from the San Francisco station, which also had picked up the code messages, and had radioed him at once the line along which they had come. Ventura had not, for some freakish reason, been able to pick up the messages at all.

It was then he had radioed Inspector Burton aboard the Bear, and caused the latter to return.

Later, however, and very recently, in fact, he had gotten information more definite. For, since Inspector Burton had telephoned him to descend from the mountains and confer at the hotel, he had picked up another message in code in which, moreover, occurred the words “Santa Cruz” several times.

“So there you are, Inspector,” he said. “That’s what the Bender sound detector discovered. Human ingenuity could do no more.”

“You certainly have done wonders, Mr. Bender. It is your opinion, then, that the smugglers’ radio plant is on Santa Cruz Island?”

“It seems so to me,” said the inventor, nodding with vigor.

Inspector Burton was thoughtful. The others remained silent, waiting for him to speak.

“I believe you are correct,” he said at length. “Ensign Warwick, what do you say?”

“It certainly looks as if Santa Cruz is the smugglers’ hangout.”

“And you, Mr. Temple?”

The latter smiled and shook his head.

“I have no opinion one way or the other,” he said.

Then Inspector Burton turned to the boys.

“Well, lads,” he said. “I have a proposition to make to you. I really believe we have located the smugglers’ hangout; that it is on Santa Cruz Island. And, while it is a big island, yet the smugglers’ headquarters undoubtedly must be on the seaward side, as I earlier explained, and there are not many places on that rocky shore where a landing could be made.

“I was fortunate on arrival yesterday to get in touch with an old Mexicano, a native of this country, who at one time many years ago tended cattle on Santa Cruz Island when an early-day rancher attempted to maintain a cattle ranch there. He found the grazing too poor to make the venture profitable and gave up his project. This old fellow, whom I located down in the Mexican quarter of the town, gave me much valuable information.

“For one thing, I questioned him closely as to the possibilities for making a landing on the seaward side of Santa Cruz. He said there was only one place really practical, and that was the mouth of a creek near the western extremity of the island. At other places, he said, cliffs descended abruptly to the sea, and the waves always were high. Boats could not safely land.

“Now, if the smugglers are on Santa Cruz Island that must be their location—up that creek. The ships can stand off shore, while small boats ply back and forth between the ship and the creek, landing the smuggled Chinese coolies. Probably, somewhere up the creek, the smugglers have a number of rude barracks, providing temporary shelter for the Chinese until they can be dispersed to the mainland. Also their radio plant must be up there.”

He paused, and Frank eagerly asked the question trembling on the lips of all three chums.

“You said you had a proposition to make us, Inspector?”

The Secret Service man smiled.

“Yes, I have a proposition,” he said. “Briefly, would you care to accompany us tonight on an expedition to Santa Cruz?”

“Would we?”

All three expelled the exclamation simultaneously.

Inspector Burton turned to Mr. Temple.

“These boys have shown such ingenuity so far,” he said, “and have been of such aid, that I feel I owe it to them to take them along. Of course, they must have your consent. And I would be delighted to have you with me, too, if you would care to come.”

“Not I, thank you,” said Mr. Temple, with emphasis. “And I don’t know about consenting to your request in regard to the boys. It is very kind of you, and I can see you sympathize with their adventurous inclinations. But, won’t it be dangerous? Won’t the smugglers put up a stiff fight?”

“There is that possibility, of course,” said Inspector Burton. “I believe, however, that when they see the uniforms of Uncle Sam’s fighters, and discover an armed vessel of the navy off shore, they will surrender without resistance. Most folks, you know, have a great horror of running foul of the government and its armed forces. Police they might resist, but Uncle Sam’s sailors and soldiers overawe them.”

“Yes, I believe that is true,” said Mr. Temple. “Still——”

“However, Mr. Temple,” said the Secret Service man, hastily, “I can sympathize with your anxiety, and if you object I withdraw my invitation to the boys.”

“Dad, you have got to let us go,” pleaded big Bob. “Why, as Inspector Burton says, there will be little danger. Besides, we aren’t babies. We have taken care of ourselves pretty capably under trying circumstances this summer, haven’t we? Now, haven’t we?”

He stood above his father as he spoke, having leaped to his feet in his anxiety.

“Yes, you have, Bob,” said his father. He put up his hands before him as if for protection, and bent away in mock terror from his big son. “Don’t strike. I surrender.”

The three chums shouted with delight.

“But, remember,” Mr. Temple warned. “I want you to go on this expedition, bearing the same advice the mother gave her daughter. You may ‘hang your clothes on a hickory limb, but don’t go near the water.’ In other words, if there is any fighting, stay out of it. Unless, of course, you are personally attacked, or your side is hard pressed.”

“Righto, Dad. We’ll remember,” said Bob.

“And now, boys,” said Inspector Burton, “I have my arrangements to make. So, if you will meet me at the pier—or, better, aboard the Sub Chaser—at seven o’clock tonight, I’ll excuse myself.”

He arose, asking Ensign Warwick to accompany him.

“As for me,” said Mr. Temple, when the two officers had left the room, followed by Inventor Bender, “I’m worn out, and am going to take a nap. You boys have two or three hours of spare time. It would do you all good, in view of your trip tonight, to try to snatch a few hours’ sleep. But I suppose it would be impossible for you to compose yourselves?”

“Couldn’t be done, Dad,” agreed Bob. “We’ll go out and look at the town for an hour or so. We can be back around five-thirty, get a bit of dinner, with you, and then go to the boat.”