Three hours later he was back on post. Quickly he explained to his prisoner all about the workings of the submarines of the expedition. The lights-out bell rang, and all the city became dark, except for dim lights in the passageways. Hakin at once unlocked the door of Abbot's cell, and together the two young men sneaked down the corridor to the cell where Milli was confined.
Silently Hakin and Abbot sprang upon the guard and throttled him; then released Milli. There was no time for more than a few hurried words of explanation before the three of them left the prison and made for the locks of the subterranean canal, picking up Romehl at a preappointed spot on the way.
he canal locks were unguarded, as well as the storerooms of the submarines. Each of the rooms held two subs, and could open onto the second lock and be separately flooded.
The submarines were of steel as thick as Abbot's bathysphere. Their shape was that of an elongated rain drop, with fins. In the pointed tip of their tails were motors which could operate at any pressure. At the front end were quartz windows. In the top fin was an expanding device which could be filled with buoyant gas, produced by chemicals, when the craft neared the surface. Each submarine also contained a radio set, so tuned as to be capable of opening and closing the radio-controlled gates of the locks. Each would carry comfortably two or three persons.
Having picked out two submarines and found them to be in order, Hakin sneaked back into the corridor to set off the time-fuse, leaving his three companions in the dark in the storeroom. Abbot put a protecting arm around Milli, while Romehl snuggled close to her other side.
Their hearts were all racing madly with excitement, and this was intensified when they heard Hakin talking with someone just outside their door.
Then Hakin returned unexpectedly.
"Something terrible has happened!" he breathed. "The explosives have been discovered and are gone. One of the expedition men has just informed me. Someone must have gotten word to Thig—"