both hands by the throat.

Before he could tighten his grip came a tremendous shock, and he was flung
off the other as if by a giant's hand. As he rolled across the floor,
followed a crash as though the very heavens were falling. The whole ship
seemed to lift beneath him, at the same time stopping short as though she
had hit a cliff.

[Illustration: 'Ken flung himself on the signaller.']

For an instant there was dead silence. Then from the decks above came
shouts and a pounding of feet. Half stunned, Ken struggled to his feet,
and staggered towards the door. As he did so, he heard the click of the
latch, and before he could reach it, it was banged in his face.

Groping in the darkness, he found the handle. He turned it, but the door
would not open. In a flash the truth blazed upon him. He was locked in.
The spy had locked the door on the outside. He was a helpless prisoner in
a torpedoed and probably sinking ship.

CHAPTER II

THE LAST OF THE 'CARDIGAN CASTLE'

Ken's head whirled. For the moment he was unable to collect his ideas. He
stood, grasping the door handle, listening to the thunder of feet overhead
and the shouted orders which came dimly to his ears.

He heard distinctly the creaking of winches, and knew that the boats were
being lowered. His worst suspicions were true; the ship was actually
sinking.

This lasted only a few seconds. Ken Carrington was not the sort to yield
weakly to panic. He pulled himself together, and felt for the switch.

It clicked over, but nothing happened. The shock of the explosion had
evidently thrown the dynamo out of gear. Then he remembered the little
electric torch which he always carried, and in an instant had it out of
his pocket, and switched it on.

He flashed the little beam across the floor, and its light fell upon the
wooden grating over which he had stumbled in his first rush at the enemy
signaller. This lay alongside the bath. It was about six feet long and
made of four heavy slats nailed on a framework.

It took Ken just about five seconds to lay down his lamp and heave up the
grating.

Short as the time had been since the first shock of the torpedo, the ship
was already beginning to list heavily. The floor of the bathroom now
sloped upwards steeply to the door.

The grating was very heavy, but in his excitement Ken swung it up as
though it had been no more than a feather. Balancing it, he charged
straight at the door.

The end of the grating