The whistle was like that of a man who is not thinking much of what he is doing, but it had a penetrating quality which is not often heard in that sort of music.
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.