He gave the signal and the D-16 started in pursuit.

Frank held a consultation with the German prisoner.

“I believe,” said the latter, “that the Russian has refused to accept your commander’s explanation and has had him and his first officer placed under arrest.”

“By Jove!” said Frank. “I hadn’t thought of that. I wouldn’t be surprised if you are right.”

He gave the order for full speed ahead, and gradually the submarine began to overhaul the Russian cruiser. As he came nearer, Frank perceived signs of action aboard the larger vessel, and then he was hailed across the water.

“Sheer off, or we shall fire into you.”

“Don’t you try it,” cried Frank, angrily. “Where is my commander?”

“He is a prisoner,” came back the reply, “and has given his parole not to escape.”

“Let me speak to him,” demanded Frank.

When this command was taken to the Russian commander, he hesitated. But at length he decided to allow Lord Hastings to hail the D-16.