A lew weeks ago, a $oston detective cailed at the Fifth Avenue Theater, and explainod to Mr. Stephen Fiske that he was in confldential communication with Mis. Moher, the widow of the man who had stolen Charley Koss ; that she was evidently exeroised in rnind in regard to the secret of the boy's fate ; that she had heard of the stolen child in " Pique," and was anxious to see the play if she could come to the theater unobserved ; and he believed that, under the influence of the play, she might be induced to make the confession which she had hitherto refused. These facts having been represented to ;Mr. Daly, he placed his own private box at the service of the detective, and the nezt evening Mts. Mosher was brought quietiy to the theater. Shc was a plain, elderly woman, neatly attired in black, and was accompanied by a f emale f riend. Duiiug the progresa of the trial she laughed and cried with the rest of audienco, but di'l not exhibit any special porturbation until the last act. The sorrow of the herome, Miss Fanny Davenport. then appeared to move her strangely. When Miss Davenport exclaimed : "He'sdead!" Mrs. "Mosher rockod herself backward and forward and rcpeated : " He's dead ! Yes, he's dead !" The joy in the Iienfrew family when the stolen ehild was restored also afl'ected her deeply. At the close of the performance Mrs. Mosher and tho detective lef t the theater as quietiy as they had entered, the detective whipering to Mr. Fiske as they passed, " I think it has been a success." No further rovelations were vouchsafed until Wednesday, when Mr. Ohristian K. Bobs, tho father of the abducted boy, visited Superintendent Walling, and held a long conference in refcrence to somo new clews which have been discovered. It is believed Communications have passed between Mrs. Mosher and her brother, Wcstervelt, now under sentence in Moyamensing Prison, and that the fate of Chariey Boss is shortly to be cleared up.