midnight
In fact , he did not seem at all desirous of having any conversation with them , for , with the exception of taking a short walk about the island after every meal , he passed both day and night in dozing in the cabin . 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 .