As the night fell the wind rose and moaned dismally over the marsh, and black clouds covered the sky, so that the night promised to be dirtier than usual at this time of the year. Lonely marshes stretched far and wide, with nothing to break their wild monotony save the ghostlike ruins of the Abbey in the foreground. It was not a pleasant night for the boys to spend out for the first time alone, and an eerie sort of feeling crept over them in spite of their efforts to appear at ease. At length Dick said-- "I feel as if wild beasts were prowling about on the watch for us, and that if we went to sleep we should be eaten up alive." "So do I," admitted Frank; "but I suppose it will wear away in time. But what is that?" he exclaimed, in a startled tone, as an unearthly cry sounded among the ruins of the Abbey, and a white shape was dimly seen gliding between the broken windows. The boys gazed in breathless silence at this apparition. The cause of their alarm, however, was made plain to them, as a white owl came forth on noiseless wings, and fluttered stealthily over the marsh. They laughed heartily at their fright, but their laugh sounded forced and unnatural. It was so weird and lonely outside, that they went into the cabin and lit the lamp, and strove to make a cheerful supper. Then they undressed and tried to make themselves comfortable for the night. Frank took the hammock, and Dick and Jimmy the berths at each side. They left the lamp burning dimly for company's sake, but they could not go to sleep. The water lapping against the planks of the yacht and amid the stems of the reeds, the wind sighing over the waste fen, and the strange cries of the night-birds--the call of the water-hen, the hoarse bark of the coot, the cackle of wild ducks, and the host of other noises which they could not account for, kept them awake and on the _qui vive_. "What's that?" said Dick, after they had been quiet for some time. [Illustration: THE BARN OWL AND EGG.] A noise like a clap of thunder was to be heard, repeated at regular intervals, and growing louder, as if approaching them. They rushed on deck to see what was the cause of it, and were relieved to find that it was only a belated wherry beating up to windward, her canvas flapping each time she put about on a fresh tack. The men on board of her shouted "Good night" as they passed, and after this the boys felt more comfortable, and again courted sleep. They were just dropping off, when "patter, patter," went something on deck. Some one, or some thing had boarded them, and Frank went out to see what it was. A coot had come aboard to see if there might be anything eatable there, and she flew away as Frank appeared. He looked about ere he went down again, and to his astonishment he saw a spot of light dancing about on the marshes in a place where he thought no human being could be at this hour. "I say, Dick and Jimmy, here is a will-o'-the-wisp dancing about on the marshes."