Members of Nick Carter’s household all declared that they would know his whistle whenever they heard it, no matter what tune it might give forth--or even no tune at all. The detective was testing the truth of this assertion at this moment. There was short pause as he finished the line of “Tipperary,” and then, in answer, came another part of the melody, taking it up where he had left off. The person whistling in response was somebody that Nick Carter could swear to. He smiled gently in the darkness. “Chick, by all that’s lucky!” he muttered. “He’s in that boat, and he knows I’m here. Well, that means I must get out of this stateroom without loss of time.” He whistled again, but shut off in the middle of a measure. This was a code signal between them, meaning “Wait!” Quite well assured that Chick would wait till he heard again from his chief, and that he would contrive to keep out of sight of any watchers who might be on the yacht, Nick went to the door, a small wire in his fingers. It was with this wire that he intended to open the door, and in a few minutes he had proved that he could carry out his intention. The lock shot back with a faint click, and there was nothing to prevent his opening the door when ready. He stood just inside and listened intently for at least two minutes. Then he turned the handle softly and looked out into the corridor. It was empty. One electric light cast a dim light from end to end. It showed Nick the way to the outer door. There was a short flight of brass-bound steps and a heavy door. Beyond was the deck. What would he meet when he opened that door? That was the question he asked himself, as he took his automatic pistol from its waterproof case, and made sure it was charged with cartridges, ready for action. The mocking smile which had been on his face during the interview with Don Solado, and which had not quite faded as he sat in the darkness, was gone entirely now. Stern business was the expression--that and nothing else. On the deck he met nobody. He was overlooking the taffrail. In the shadows beyond he made out the boat in which sat his assistant. Nick whistled another line of “Tipperary,” and at the same time sent a short flash of light from his pocket electric lamp in the direction of the small boat. There was immediate response in the shooting forward of the boat until it was directly below where Nick stood leaning on the rail, looking down at the water. The detective had not been idle during the approach of Chick’s boat. He had found a coil of light rope and fastened one end to the rail. The other dropped to the water. “Chick?” he whispered. “That’s who it is, chief!” was the prompt reply. “What shall I do? Come up?” “Yes. But first make sure your boat won’t get away. Make it fast to a rudder chain.” It took Chick only a fraction of a minute to do this. Then he seized the line and gave it a tug to test its strength. “It will hold you all right,” whispered Nick. “Come on!”