Hundreds of ships, large and small, had fallen easy prey to these under-sea terrors. Big ocean liners, crowded with passengers, non-combatants, had been sent to the bottom with terrible loss of innocent lives. Chief among these tragedies laid to the door of the German submarines was the sinking of the Cunard liner Lusitania, in which more than a thousand men, women and children had been drowned.
And, so far as the British public knew, England had taken no steps to combat this under-sea peril. However, as Lord Hastings had told the boys at the opening of this story, Great Britain had taken such steps, and that they were effective was evident from his additional statement that in the neighborhood of a hundred submarines had "vanished."
But this warfare was not to end until the submarine evil had been eradicated. The German under-sea craft must be disposed of so effectively as to preclude further danger to British shipping. And it was in this work that Jack and Frank were soon to play a prominent part.
CHAPTER II.
ON ACTIVE SERVICE AGAIN.
For some reason unknown to Jack and Frank, when morning came, Lord Hastings announced that the start would not be made until after nightfall, at which both lads showed keen disappointment.
"I'll tell you what you can do," said Lord Hastings. "I'll give you an order for my motorboat and you can go to Gravesend during the day if you care to. I'll meet you there at the Lion Inn to-night at 10 o'clock."
Frank was delighted.
"That's better than hanging around here all day, waiting for night to come," he said. "What do you say, Jack?"