rboat."

"That's what bothers me," Rick replied. "There's no pattern. It just
makes no sense."

"It doesn't have to," Tony Briotti said with a grin. "The Golden Skull
pattern makes no sense, either. But you got us into more excitement than
I knew was possible. You're just adventure-prone."

"And for the sake of my gray hair, stay out of trouble," Zircon pleaded.
"Stay close to us until we get to Clipper Cay."

"It will be a pleasure," Rick assured him. "Only let us out of your
sight long enough to shower, please. I'm sticky."

"We'll stay in the hotel," Scotty promised.

"Fine. I'll feel better about it if I know where you are. Suppose you
come by in an hour and we'll have a quiet dinner at the Ernsts'."

Dinner was quiet but interesting. The Ernsts were excellent hosts, and
both Dr. and Mrs. Ernst had many tales of the islands to tell. As the
good doctor had promised, the boys enjoyed the wonderful variety of sea
life Mrs. Ernst had collected to keep in salt-water tanks. She
identified for them a number of the smaller reef fishes, including
clowns, demoiselles, and even the deadly scorpion fish.

The party broke up early, since the start for Clipper Cay was to be made
at dawn by the scientists. The plan was for Zircon and Tony to make the
trip in the _Water Witch_, with the boys flying over in the Sky Wagon.
That way, both the plane and boat would be available. Zircon thought
that fast trips to St. Thomas might be necessary to replenish supplies,
and he added that he would be happier if the plane were available in
case of accident. That way, the patient could be in Charlotte Amalie in
a short time.

As the boys bade good night to the scientists and started up the stairs
to their room, Rick asked, "Any sign of a shadow tonight?"

"Nope. Guess Steve's friends--or enemies--must have lost interest."

"I hope that you're right. As long as Steve ordered us to stay out of
the case, I'll be glad when we get to the cay and get underwater. We
have to find that precious gadget even if it takes two solid weeks of
diving. If we don't, Barby will never let us forget it."

This last was uttered as Rick turned the key in the lock and pushed the
door open. He flicked on the light, then gave a sudden gasp.

The shadow and a stranger--in their room!

The boys looked into the muzzles of .38-caliber pistols.

"Come on in quietly," the stranger said. "Put your hands on the tops of
your heads and sit down on the bed over the