"We can't just float around and talk," Scotty said urgently. "Let's do something." Rick felt the same way. "Okay. Throttle down and go slow. We'll scan the whole coastline from here to Spindrift." Scotty did so, holding the little plane barely above stalling speed. Rick leaned out and traced the shore with anxious eyes. The plane turned and twisted as Scotty followed the coastline as accurately as he could. They reached the upper tip of North Cove and swung into the cove itself. Scotty tapped Rick on the shoulder and pointed. A man and a woman had come out of the houseboat and were watching the plane. "Wonder where the other pair is?" Rick asked. There was nothing they could do about the people on the houseboat now. Let them wonder what the plane was doing. Rick turned his attention back to the shore below. The plane traveled the length of the cove's shoreline and rounded the southern tip. They passed over a section where the woods came right down to the water. Birches leaned far over. Rick caught a glimpse of what might have been the rowboat, then the plane swung and he lost it. "Circle," he said quickly. "I think I saw something!" Scotty gunned the Sky Wagon and threw it into a tight turn. Rick watched carefully as the clump of birches came into view. There was a boat under them, all right. He wished for the binoculars, but they were probably at the attic lookout where Barby and Jan had spied on the houseboat. He had no real doubt. He was sure the boat was the Spindrift rowboat. "Circle over the island," he called to Scotty, then reached over and took the hand microphone from the instrument panel rack. He turned on the radio and waited a moment while it warmed. "Joe, this is Rick," he said. "Rowboat under a clump of birches just south of North Cove. Have the boys go there and look it over. See if the girls are in the woods. We'll watch for sign of the girls on the water." To Scotty, he directed, "Over the cove. Circle the whole area. We'll watch for their bubbles. Joe's men will check the woods." The plane turned obediently. Presently they were moving in a wide circle with the houseboat as a center. A slight surface wind had arisen and the water in the cove was a bit choppy, but not enough to obscure bubble tracks made by Scuba divers below. "See anything?" Rick asked. "Not a trace. Can you see the water around the houseboat well enough?" "Yes. No bubbles in the vicinity." Rick dried his palms again, then mopped his forehead. He was becoming thoroughly frightened. Where were they? He checked his Megabuck radio to be sure it was on and called, "Barby. Where are you?" The air was silent, except for the slight background hiss that was always present. "Look right under the houseboat's gunwales," Scotty urged. "If they're directly under it, the bubbles would rise along the sides." "Why would they go under the houseboat?" Rick asked. Scotty shook his head. "Why did they come over here in the first place?"