Rick looked up. "What are you trying to find?"

"Periodicity," Steve said promptly. "Is there any regularity in the sightings? Do they occur every three, four, or five days, or once a week on Mondays? Which reminds me. You might put down the day of the week, too. There's a calendar on the wall behind you."

"You read and I'll copy," Rick told Scotty. "Go ahead." He waited with pencil poised over a card. In a moment he looked at his pal. "What are you waiting for?"

Scotty was poring over the notebook again. His eyebrows knit. "You know, there's one chunk of data on just a few sightings that we didn't put down because we didn't have a column for it."

"What is it?" Steve asked.

"I know!" Rick exclaimed. "There were a few times when people said they saw yellow glows in the sky after they saw the objects. Isn't that it?"

Scotty nodded. "I've been counting. There were five instances. Two people said the glow wasn't really connected, because it came from Wallops Island."

"Why on earth didn't you include it in the chart?" Steve demanded.

"It doesn't fit," Scotty replied. "In every single case, the glow was to the southeast."

"Maybe it does fit," Steve said emphatically. "Boys, never leave out a bit of data because it doesn't seem to fit. This particular chunk could very well be the clue."

"Why?" Rick asked quickly.

Steve shook his head. "I'm not sure, so I don't want to say. But include every sighting of the yellow glow on the date cards. I'm going to borrow that set for a closer look."

Scotty began reading, while Rick recorded. When the cards were complete, they ran through them. There was no periodicity. The dates seemed completely random. Sometimes two sightings had been made at different times on the same date. There would be two days, three, four, five, or even six between sightings.

"Not a trace of pattern," Rick said.

"Who says stingarees have to fly on schedule?" Steve asked with a grin.

"They're not supposed to be like planes. What's the next step?"

Scotty produced the map they had used. "One more job to do, and that's to plot the locations of the observers and draw lines in the directions of the sightings. That will show us if there's any regularity in the place where the flying objects appear."

"Very good," Steve approved.

Scotty took pencil and ruler and laid the map out flat. "You read location and direction, Rick, and I'll plot the data."

"Okay." Rick began with the first. "Five miles south of Wye Mills on Route 50. Direction, southwest."

Scotty measured the distance from Wye Mills, using the map scale in inches, then estimated the compa.s.s direction and drew a line. "Next."

Rick read on. By the time he had reached the tenth sighting, all three of them were waiting anxiously for each new bit of data to be plotted.

Finally the job was complete. Steve had hurried off a moment before and returned with a pair of compa.s.ses in his hand. As the boys watched, he put the sharp point of one compa.s.s leg into a spot on the map, adjusted the radius, and drew a perfect circle. He adjusted the radius again, and drew a second circle, slightly larger, then a third.

"Bull's-eye!" Rick said excitedly.

The direction lines bisected the outer concentric circles like the radii of an orb spider's web. In the center of the web was the smallest circle. Within the circle was the focal point of all flying object observations.

Rick said the name aloud.

"Swamp Creek!"

CHAPTER VIII

Calvert's Favor

There was a faint hint of coming daylight in the eastern sky when Rick, Steve, and Scotty walked down the pier to the tied-up boats. The boys had spent the night--or most of it--aboard the houseboat, until the alarm pulled them from their sleeping bags at four o'clock. Steve had breakfast cooking when they arrived at the farmhouse, and after coffee, bacon, and eggs, they started on their mission.

"Daybreak is the lowest peak of daily activity," Steve said as they climbed into the runabout. He took the pilot's seat, while Rick and Scotty prepared to cast off.

"You might say that the first glimmer of daylight is man's worst hour,"

Steve continued. "It's the time when battles start, when planes take off for dawn bombing runs. I've read that it's the time when most deaths occur in hospitals, although I don't know for certain that it's true.

What's more important to us, it's the time of day when guards are most sleepy and least alert."

The young agent had been working as he talked, checking the outboard motor, checking the connections to the gasoline tank, and pumping pressure into it. Now he pressed the starter and the well-kept motor caught at once. Rick and Scotty cast off bow and stern lines and settled themselves in the seat next to Steve.

"Unless this mysterious Mr. Merlin suffers from sleepless nights, he's deep in slumber. The sound of a small boat won't disturb him, because he's used to the noise of motors from crabbers. We'll hope there is no guard on the place. If there is, we'll be fishing. Better have the rods ready. One of you can sit in back and troll from there."

The outboard runabout moved away from the pier and into the creek. Steve knew his way perfectly, and he opened the throttle to half speed, steering through the curve at the mouth of the creek, rounding the buoy, and heading directly toward Swamp Creek.

It had taken the houseboat over twenty minutes to make the run. Steve covered the distance in ten. As he throttled down and swung the runabout into Swamp Creek, Rick's eye picked up a glimmer of light, then the shape of something white cruising toward them.

For a moment he stared into the lessening gloom, then said, "It's Orvil Harris. Anyway, it looks like his boat."

Steve said nothing for a moment, then he headed directly toward the crabber. As the two boats closed, Harris paused in his crabbing and watched the three in the runabout approach.

Steve matched the crab boat's speed and nudged the runabout alongside.

"Howdy," he called.

Orvil Harris reached out and caught the runabout's gunwale, then took the line Rick pa.s.sed to him. He made it fast around a cleat. "Up early,"

he greeted them. "Come to watch me crab?"

"Not exactly," Rick returned. "Mr. Harris, this is Mr. Ames."

The crabber reached out a muscular hand and Steve stretched to meet it.

"Mighty pretty place you have on Martins Creek," Harris said. "Admired it many's the time."

"Thanks," Steve returned. "Be glad to have you drop in any time."

"I may do that. Thanks."

"The boys tell me your cousin was the one taken by a flying saucer."

Harris grinned. "He was taken. I'm not sayin' how until I know."