"But they don't say the door opens every time you knock," Furuneo said.

McKie continued working his way around the Ball, found another nippled extrusion, knocked.

Nothing.

"We tried that one, too," Furuneo said.

"I feel like a damn fool," McKie said.

"Maybe there's nobody home."

"Remote control?" McKie asked.

"Or abandoned - a derelict."

McKie pointed to a thin green line about a meter long on the Ball's windward surface. "What's that?"

Furuneo hunched his shoulders against spray and wind, stared at the line. "Don't recall seeing it."

"I wish we knew a lot more about these damn things," McKie grumbled.

"Maybe we aren't knocking loud enough," Furuneo said.

McKie pursed his lips in thought. Presently he took out his toolkit, extracted a lump of low-grade explosive. "Go back on the other side," he said.

"You sure you ought to try that?" Furuneo asked.

"No."

"Well -" Furuneo shrugged, retreated around the Ball.

McKie applied a strip of the explosive along the green line, attached a time-thread, joined Furuneo.

Presently, there came a dull thump that was almost drowned by the surf.

McKie felt an abrupt inner silence, found himself wondering, What if the Caleban gets angry and springs a weapon we've never heard of? He darted around to the windward side.

An oval hole had appeared above the green line as though a plug had been sucked into the Ball.

"Guess you pushed the right button," Furuneo said.

McKie suppressed a feeling of irritation which he knew to be mostly angeret effect, said, "Yeah. Give me a leg up." Furuneo, he noted, was controlling the drug reaction almost perfectly.

With Furuneo's help McKie clambered into the open port, stared inside. Dull purple light greeted him, a suggestion of movement within the dimness.