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 shore 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?”