"Oh for a respirator!" whispered O'Hara.
"Don't worry," said Stirling. "The electric fan will carry off the fumes as quickly as they pump them in."
Even as he spoke the fan ceased to revolve. The current actuating the ventilating gear had been switched off. Already Unter-leutnant Klick was putting his scheme into effect.
"Those voice tubes," hissed Denbigh.
"They lead nowhere," protested Stirling. "They are blocked. I tried them some time ago."
The cabin had previously been used as the purser's office, and from it voice-tubes had communicated with the captain's cabin, the head steward's quarters, and the clerk's office. The metal pipes had been removed, but three lengths of flexible tubing had been left.
With a sharp tug Denbigh wrenched one of the tubes from the flange securing it to the bulkhead. The second gave more trouble. As he was straining at it a sharp rasping sound fell upon his ear. In the adjoining cabin someone was at work drilling a hole through the metal partition.
Smearing the bell-shaped mouth-pieces of two of the detached pipes with soap from the wash-basin, Denbigh clapped them together.
"Hold on here, Pat," he whispered. "Press 'em tightly."
O'Hara obeyed unhesitatingly. Instinctively he realized that this was Denbigh's pigeon, and once Denbigh undertook a task he was pretty certain of the result.