Read it through once

“Excellent! We shall then look thoroughly into the affair. Of course there is only one feasible explanation. You have been brought there to personate someone, and the real person is imprisoned in this chamber. That is obvious. As to who this prisoner is, I have no doubt that it is the daughter, Miss Alice Rucastle, if I remember right, who was said to have gone to America. You were chosen, doubtless, as resembling her in height, figure, and the colour of your hair. Hers had been cut off, very possibly in some illness through which she has passed, and so, of course, yours had to be sacrificed also. By a curious chance you came upon her tresses. The man in the road was undoubtedly some friend of hers—possibly her _fiancé_—and no doubt, as you wore the girl’s dress and were so like her, he was convinced from your laughter, whenever he saw you, and afterwards from your gesture, that Miss Rucastle was perfectly happy, and that she no longer desired his attentions. The dog is let loose at night to prevent him from endeavouring to communicate with her. So much is fairly clear. The most serious point in the case is the disposition of the child.”