"Engines started, sir," said the voice of Angus Munroe.

Looking back at the planes I saw that the propellers had vanished. There was a soft whirr, a soughing like a wind in trees, and a very slight tremor through the structure of the boat.

Pank looked at the row of indicators on the wall. All had a white disk down except in the spaces numbered two and three. "Seal doors two and three," he ordered. The two white disks dropped in the indicators.

"Bow-man, stand by to let go."

"Aye, aye, sir."

"Engines. Stand by for four seconds half blade on port propellers."

"Standing by, sir."

"Bow-man, let go."

"All gone, sir."