There--it has gone."

We continued to watch for several minutes, but it did not reappear.

Could it have been a light on the mast of a boat moving rapidly up the bay and perhaps nearer to us than we suspected? Nothing further happened, however, and we retired early, expecting to start with fresh minds on the case in the morning. Several watchmen whom Verplanck employed both on the sh.o.r.e and along the driveways were left guarding every possible entrance to the estate.

Yet the next morning as we met in the cheery east breakfast room, Verplanck's gardener came in, hat in hand, with much suppressed excitement.

In his hand he held an orange which he had found in the shrubbery underneath the windows of the house. In it was stuck a long nail and to the nail was fastened a tag.

Kennedy read it quickly.

"If this had been a bomb, you and your detectives would never have known what struck you.

"AQUAERO."

CHAPTER V

THE ULTRA-VIOLET RAY

"Good Gad, man!" exclaimed Verplanck, who had read it over Craig's shoulder. "What do you make of THAT?"

Kennedy merely shook his head. Mrs. Verplanck was the calmest of all.

"The light," I cried. "You remember the light? Could it have been a signal to some one on this side of the bay, a signal light in the woods?"

"Possibly," commented Kennedy absently, adding, "Robbery with this fellow seems to be an art as carefully strategized as a promoter's plan or a merchant's trade campaign. I think I'll run over this morning and see if there is any trace of anything on the Carter estate."

Just then the telephone rang insistently. It was McNeill, much excited, though he had not heard of the orange incident. Verplanck answered the call.

"Have you heard the news?" asked McNeill. "They report this morning that that fellow must have turned up last night at Belle Aire."

"Belle Aire? Why, man, that's fifty miles away and on the other side of the island. He was here last night," and Verplanck related briefly the find of the morning. "No boat could get around the island in that time and as for a car--those roads are almost impossible at night."

"Can't help it," returned McNeill doggedly. "The Halstead estate out at Belle Aire was robbed last night. It's spooky all right."

"Tell McNeill I want to see him--will meet him in the village directly," cut in Craig before Verplanck had finished.

We bolted a hasty breakfast and in one of Verplanck's cars hurried to meet McNeill.

"What do you intend doing?" he asked helplessly, as Kennedy finished his recital of the queer doings of the night before.

"I'm going out now to look around the Carter place. Can you come along?"

"Surely," agreed McNeill, climbing into the car. "You know him?"

"No."

"Then I'll introduce you. Queer chap, Carter. He's a lawyer, although I don't think he has much practice, except managing his mother's estate."

McNeill settled back in the luxurious car with an exclamation of satisfaction.

"What do you think of Verplanck?" he asked.

"He seems to me to be a very public-spirited man," answered Kennedy discreetly.

That, however, was not what McNeill meant and he ignored it. And so for the next ten minutes we were entertained with a little retail scandal of Westport and Bluffwood, including a tale that seemed to have gained currency that Verplanck and Mrs. Hollingsworth were too friendly to please Mrs. Verplanck. I set the whole thing down to the hostility and jealousy of the towns people who misinterpret everything possible in the smart set, although I could not help recalling how quickly she had spoken when we had visited the Hollingsworth house in the Streamline the day before.

Montgomery Carter happened to be at home and, at least openly, interposed no objection to our going about the grounds.

"You see," explained Kennedy, watching the effect of his words as if to note whether Carter himself had noticed anything unusual the night before, "we saw a light moving over here last night. To tell the truth, I half expected you would have a story to add to ours, of a second visit."

Carter smiled. "No objection at all. I'm simply nonplussed at the nerve of this fellow, coming back again. I guess you've heard what a narrow squeak he had with me. You're welcome to go anywhere, just so long as you don't disturb my study down there in the boathouse. I use that because it overlooks the bay--just the place to study over knotty legal problems."

Back of, or in front of the Carter house, according as you fancied it faced the bay or not, was the boathouse, built by Carter's father, who had been a great yachtsman in his day and commodore of the club. His son had not gone in much for water sports and had converted the corner underneath a sort of observation tower into a sort of country law office.

"There has always seemed to me to be something strange about that boathouse since the old man died," remarked McNeill in a half whisper as we left Carter. "He always keeps it locked and never lets anyone go in there, although they say he has it fitted beautifully with hundreds of volumes of law books, too."

Kennedy had been climbing the hill back of the house and now paused to look about. Below was the Carter garage.

"By the way," exclaimed McNeill, as if he had at last hit on a great discovery, "Carter has a new chauffeur, a fellow named Wickham. I just saw him driving down to the village. He's a chap that it might pay us to watch--a newcomer, smart as a steel trap, they say, but not much of a talker."

"Suppose you take that job--watch him," encouraged Kennedy. "We can't know too much about strangers here, McNeill."

"That's right," agreed the detective. "I'll follow him back to the village and get a line on him."

"Don't be easily discouraged," added Kennedy, as McNeill started down the hill to the garage. "If he is a fox he'll try to throw you off the trail. Hang on."

"What was that for?" I asked as the detective disappeared. "Did you want to get rid of him?"

"Partly," replied Craig, descending slowly, after a long survey of the surrounding country.

We had reached the garage, deserted now except for our own car.

"I'd like to investigate that tower," remarked Kennedy with a keen look at me, "if it could be done without seeming to violate Mr. Carter's hospitality."

"Well," I observed, my eye catching a ladder beside the garage, "there's a ladder. We can do no more than try."

He walked over to the automobile, took a little package out, slipped it into his pocket, and a few minutes later we had set the ladder up against the side of the boathouse farthest away from the house. It was the work of only a moment for Kennedy to scale it and prowl across the roof to the tower, while I stood guard at the foot.

"No one has been up there recently," he panted breathlessly as he rejoined me. "There isn't a sign."

We took the ladder quietly back to the garage, then Kennedy led the way down the sh.o.r.e to a sort of little summerhouse cut off from the boathouse and garage by the trees, though over the top of a hedge one could still see the boathouse tower.

We sat down, and Craig filled his lungs with the good salt air, sweeping his eye about the blue and green panorama as though this were a holiday and not a mystery case.

"Walter," he said at length, "I wish you'd take the car and go around to Verplanck's. I don't think you can see the tower through the trees, but I should like to be sure."