nd a can of gasoline.

"Want to tell us why you tried to run us down?" Rick asked.

The shadow merely stared.

"Talk," Scotty ordered, "or I'll put this spear through you."

The man spoke, and his accent was the soft speech of the island. "No,
you won't. I could explain running down swimmers by accident, but you
could never explain putting a spear through a man in a boat. You don't
want that kind of trouble."

Scotty grinned at the truth of it. "Okay," he said. "Just one thing.
Don't push us too far. Stay in the water until we're ashore, and don't
try to overtake us."

"Better heed that advice," Rick warned. "Come on, Scotty. Let's go." He
put his snorkel in place.

Scotty moved to his side. "Welcome to the hospitable waters of St.
Thomas," he said. "What say we look up some friendly sharks before we go
ashore?"

CHAPTER IV

Visitors by Night

Rick and Scotty stood on the pier and watched their erstwhile shadow row
slowly toward another pier some distance away.

"We probably should have tied him up and called the police," Rick
remarked.

"It wouldn't have gotten us anything," Scotty disagreed. "He could
always claim he didn't see us in the water. After all, it wouldn't be
the first time divers had been run over by motorboats."

"It's too late now, anyway. Let's dress, then go to the hotel and tell
Zircon and Tony about this."

As they dressed in the small cabin of the _Water Witch_, Rick spoke
aloud the question that had been bothering him. "What did he have to
gain by running us down? That's what puzzles me. It was a stupid thing
to try, because he didn't really have much chance of getting both of us,
or even one, once he failed to catch us by surprise."

"He wasn't very well prepared for murder, either," Scotty added. "No
weapons except a switch knife."

Rick nodded agreement. "He was desperate," he concluded. "Suddenly he
had to take a chance on getting us. He must have known it wasn't much of
a chance. Either he lost his head, or he wasn't very bright. What could
have made him try?"

Scotty had no answer, nor could Rick even hazard a reasonable guess.

They locked the cabin of the _Water Witch_, walked into town, and found
a taxi. Their shadow did not show up again, and if a new tail had
replaced him, the new one was too good to be spotted. However, the boys
doubted that they were being followed.

"I just don't get it," Rick said for the twentieth time. "Our friend
must have lost hi