Have you switched them off?"

Barby reached up and seemed to pat her hair slightly. "I forgot," she admitted. "Now it's off."

Rick looked at Jan. "Could you hear me through Barby's phone while I was talking?"

Jan shook her head. "No, I couldn't. I was listening, too. These are wonderful, Rick."

He smiled his thanks. "One interesting thing, though. I should have known, but it didn't occur to me. The receivers are directional."

"What's that?" Barby asked.

"Directional. The antenna is a tiny coil. When it's broadside to the incoming signal, the volume is loudest, but when it's end on, the volume is much less. So, if you can't hear well, just turn sideways.

Turn until the signal is loudest."

Scotty took his transceiver from his pocket and examined it with pride. It was no larger than a pack of playing cards, and its sensitive microphone was incorporated right into the case. The tiny antenna was a piece of stiff steel wire only two inches long. The whole gadget fitted easily into an inside coat pocket without a noticeable bulge.

Barby's rig was slightly different. The antenna ran along one edge of the plastic strip. At one end the microphone was in contact with her head just above the ear, allowing for transmission of voice by bone conduction, a new method developed by the United States Air Force. At the other end of the band a tiny speaker made similar contact. Rick had worried about the effectiveness of both mike and phone, since he had never used the types before, but the design had turned out very well.

"Pretty neat if we do say so," Scotty admitted modestly.

"For once I agree with you," Barby said generously. "Now what, Rick?

There isn't anything more to do, is there?"

"Not on these." But there was more to do along other lines. He was waiting for word from JANIG. Barby and Jan disappeared and returned in a few moments with iced drinks. The boys accepted them gratefully. It was a warm day.

"How about a swim?" Scotty suggested.

Rick was about to point out that they might have work to do when Joe Blake, the JANIG agent in charge at the laboratory, hailed him. Rick ran to meet the agent.

"The boys on the mainland didn't turn up a thing," Blake reported.

"They searched from a half mile south of the pier to a half mile north. No pram anywhere."

Rick snapped his fingers. "I had a hunch they wouldn't! Okay. I'm going to take off right now and search the coast. If that pram wasn't connected with the attack on Duke and Jerry, I'll eat it."

"Good luck," Blake said. "Let me know if you need any help."

Rick hurried back to the porch. The JANIG scout team had reported early in the morning that the pram was gone from the pier. They had been covering the Whiteside area most of the night, searching for some sign of the pair that had attacked Rick's friends, but had turned up nothing suspicious.

Then, at Rick's suggestion, they had undertaken a search for the pram.

His point was simply that he had never seen a pram in the Whiteside area--something that strangers would not have known. They might have figured that tying up in plain sight was the best way of hiding their boat. It would have been, if prams had been more common.

He motioned to Scotty. "Let's go. No sign of the pram."

Barby rose instantly. "Can we go with you?"

Rick considered, then nodded. He could see no objection to taking them on what could only be a short plane trip.

As they hurried to the plane, Scotty said, "What bothers me is, why didn't the JANIG team have someone at the landing?"

"They did," Rick replied. "I asked the same question. Their roving patrol had been by there a short time earlier, but saw nothing suspicious. After all, they can't post men everywhere. So two of them take turns keeping watch on the tidal flats, in case anyone tries to cross from the mainland directly to here. The other two keep moving."

"But it's funny anyone would attack Duke and Jerry," Barby objected.

"It isn't ... well, logical."

Rick grinned. Logic and his sister had never become well acquainted.

He answered, "Suppose the enemy had been keeping track of movements by water to Spindrift? That isn't farfetched. They could do it easily without being noticed. Then, late yesterday, they saw two men get in a boat and come to the island. They were probably watching from cover.

And what did they see?"

Jan answered excitedly, "Jerry, and a man who looked like my father!"

"That's it, Jan. So, if I guess correctly, they waited, hoping the man they thought was Dr. Morrison would come back. And he did, and they were waiting."

"Sounds reasonable," Scotty agreed. "Except for one small thing. Why attack Dr. Morrison when all they have to do is turn on a gadget and his mind goes blank?"

Jan shuddered visibly. Scotty added hurriedly, "Sorry, Jan."

"Maybe it's not that simple," Rick said thoughtfully. "If they only have to turn on a gadget, why did they need to drug Dr. Marks?"

There was no answer to that. As soon as they were air-borne, Rick headed north, searching the coastline, swinging low now and then to examine marinas where numbers of boats were tied up. Scotty kept the binoculars working, but there was no sign of a pram.

"Do you suppose it's under cover somewhere?" Barby asked.

Rick shrugged. "Maybe. They might cover it if they thought anyone would come looking for it."

"They'll surely think of that, won't they?" Barby asked.

"Not necessarily. After all, they tied up at the pier in plain sight.

I think they a.s.sumed no one would worry about a small rowboat. They just didn't know prams are uncommon."

Scotty put the gla.s.ses down for a moment and rubbed his eyes. "How far could they have come, anyway? We're miles above Spindrift, and no one would row that far."

He was right, of course. Rick admitted, "I've been racking my brains, and I can't remember whether or not the pram had an outboard motor.

Just as I was about to take a close look, Jerry yelled. Do you remember, Scotty?"

Scotty shook his head. "But even with an outboard, they probably wouldn't have come this far."

"Check." Rick swung the Sky Wagon around and headed south on a straight course to Spindrift. As the fast little plane pa.s.sed over the Brant house he throttled back and dropped lower. "Let's start the search again."

Every cove was investigated, and anything that might have been a boat was inspected carefully. Then, as they reached the summer colony north of Seaford, Barby exclaimed, "Look! There's that fancy houseboat again!"

The houseboat was putting out from land, swinging on a northerly course. Rick saw that it was powered by twin outboards and that it cruised at about fifteen knots.

Scotty yelled, "Hey! Behind the houseboat! Look at the dory they're towing!"

Rick swung low and craned his neck to see. It was! The houseboat used a pram as a tender, and the pram had its own low-power outboard motor.

"That's enough," he said with satisfaction. He kept the Sky Wagon on a southerly course until Seaford pa.s.sed below, to keep the houseboaters from thinking the plane's sole interest had been in them. Beyond Seaford, he picked up Cap'n Mike's shack across the road from the old windmill.

"Let's see if Mike's home," he said, and stood the wagon up on a wing.