But now, as the pursuers crept even closer, there came a sudden startled exclamation from ahead; and at the same moment the light disappeared.

“Fire!” cried Lord Hastings.

“Boom!”

Jack had fired the gun.

There was another startled exclamation from ahead.

“Did you hit her?” asked Lord Hastings.

“Think so, sir,” replied Jack.  “Don’t see how I could have missed at that distance.”

“We’ll cruise about a bit and see,” said Lord Hastings.

He gave the command and the motorboat slowed down.

For half an hour the little craft circled about, but there was no trace of the other boat.  All aboard flashed searchlights about the water, and the larger light in the bow was turned on, casting a bright ray over the water.

“They’ve either gone away or to the bottom, sir,” said Frank.

“And I guess it’s away,” said Lord Hastings.  “Jack must have missed.”

“Don’t see how I could, sir,” declared the lad.

“Better let me try with a revolver next time,” put in Frank.  “I know I could have landed one of them.”

“Well, they have gone.  But we’ll get them if we have to follow them for a month.”

“Who, sir?” asked Frank, who could restrain his curiosity no longer.

“Why, your fellow conspirators, Davis and Baron Blosberg.”

“Baron who?” asked Frank.

“Blosberg.  He is the man we are after.  We have evidence to prove that he is at the head of a body of spies that have been divulging our plans to the enemy.  Davis is merely one of his instruments.”

“I don’t know anything about the baron,” interrupted Jack, “but if he is anything like Davis, I haven’t any use for him on general principles.”

“He’s just a bit worse, if that is possible,” declared Lord Hastings.

“Then we shall have to get him,” declared Frank.

“Right,” agreed Jack.  “A man like that is too dangerous to be running around loose.”

“We may as well proceed then,” Lord Hastings decided.  “The chances are we shall find them at the mouth of the river.  However, we will hardly pick them up before daylight.”

And Lord Hastings was right.

Day dawned cool and grey, and in spite of their heavy oilskins, Frank and Jack were chilled to the bone from their long stay in the cold.  Several times Lord Hastings had asked them if they wished to go below and warm up a bit, but each was too interested to leave his post for a moment.

“Can’t tell what minute we may run across them, sir,” Jack had said, “and I want to get even for the miss I made a while ago.”

A slight fog rose over the water.  Lord Hastings gave an exclamation of impatience.

“Even the elements conspire against us,” he said aggrievedly.

“It’s not much of a fog, sir,” said Jack.  “It may lift at any minute.”

But it didn’t lift, and at noon was as dense as before.