He didn't know where girls kept things, and he suspected that sometimes the places weren't the same as boys might pick. But he could see no possible place that he hadn't searched. That meant Barby had her Megabuck unit with her, unless she had left it somewhere else in the house. He plugged in his earphone and called. "Barby!" There was no reply. His lips set grimly. No use wasting time here. He ran from the house, hearing the sound of the Sky Wagon as Scotty warmed it up. Joe Blake was not in sight. Rick hurried into the lab and found him watching Professor Morrison who was checking some calculations on the lab's small computing machine. "Joe, step outside with me for a moment, please." Outside, Rick explained that the girls were missing, then asked, "Can you get the plane frequency on your receiver?" "Sure. It's an all-wave job. What's the frequency you use?" Rick told him, then explained, "We don't know what's going on, so we want to be prepared. If some of your Scout leaders can move down the coast to North Cove and keep an eye on the houseboat, Scotty and I will search from the air. If we see anything, we'll let you know on the plane's radio. You won't be able to talk back, but at least you can hear us, and you can let the Scouts know." He wished his mind had worked faster. Then he could have taken Scotty's Megabuck unit and given it to Joe. But there was no time now, and this other arrangement probably would do as well. "I'll pass the word to the gang on the mainland right away," Joe agreed. Joe went back into the lab while Rick ran to Pirate's Beach. Scotty was waiting, the plane's engine turning over. Together, they launched the Sky Wagon, then climbed in, Scotty in the pilot's seat. As Scotty took off, Rick tried Barby again on the radio. "Barby, this is Rick. Can you read me?" There was no reply. "Better fly as though we were heading for Whiteside," Rick suggested. He rubbed his palms on his handkerchief. They were damp with nervous perspiration. He was not as calm as he looked. Scotty swung around on course and Rick scanned the water as they passed over the north side of Spindrift. There was no sign of the rowboat yet. The plane traveled in a straight line right across North Cove. The houseboat was at anchor a few hundred yards offshore, and the pram was tied up to the rear rail. There was no sign of life. The boys reached the Whiteside pier without seeing the girls or the boat. Scotty put the plane into a tight circle and looked at Rick helplessly. "Now what?" "They can't have gone far," Rick mused. "Not in the rowboat." "They had the aqualungs," Scotty pointed out. "They must have expected to use them." "Right. But how? If they planned to get aboard the houseboat, they wouldn't be using the aqualungs. Or would they?" "Search me." "Wouldn't they just row up to the houseboat on some excuse or other? I wish I'd looked. Barby might have taken those clothes Dad wore home last night."