The rebels, on the other hand, appeared to believe him a "Yankee," and as such, considered him beneath their notice.

Frank was beginning to think that his fears had been utterly groundless, when, on the third night, he was fortunate enough to detect a plot, which, if carried into execution, would have put an end to all his hopes of seeing home again, perhaps forever.
It was his duty to stand sentry from dark until midnight.

As he walked his beat, listening for the signal of the negro, whom he every moment expected with another supply of provisions, and thinking over the scenes through which he had passed since he had entered the service, he heard a slight rustling in the bushes back of the cabin, and saw one of the deserters disappear among the trees.

What could the man mean by moving about the island at that time of night?
There must be something wrong, for his stealthy movements proved that he did not wish to be observed.

While Frank was pondering upon the subject, and debating the propriety of informing the major of the fact, the lieutenant sauntered leisurely up to the place where he was standing, and, stretching his arms, languidly inquired: "Don't you think it is very sultry this evening?
It is impossible for me to sleep." This was something unusual for the lieutenant, who, although he had often conversed very freely with the major, had never before spoken to Frank since the night of his capture.