The young diplomat Phelps is spending a few days at his fiancée's in the country, when he is suddenly called to London by his Minister to copy some very important documents. Phelps is accompanied to London by his future brother-in-law, Harrison, who must see a creditor and try to get an extension, but the creditor insists on being paid immediately. Harrison is embarrassed, he must get money. Phelps stepped out of his office only a moment and upon his return finds that the very important document is stolen. This so affects his mind that the Minister of War has him taken to his fiancée's home and lodged in her brother's room, where Sherlock Holmes comes to see him, called by Miss Harrison. During the night Phelps believes he has a nightmare. He has seen a ghost in his room. Everybody believes that he has hallucinations. Sherlock thinks the matter over and decides to take Phelps with him to London. Sherlock returns the following night and sees a shadow enter the room, open a little trap in the floor out of which he pulls something. As he passes the window, Sherlock springs at him and after a struggle, seizes a paper which proves to be the stolen document. He also secures the ring of the man who was playing the ghost. The following day there is a dinner at Sherlock Holmes', the document is brought in on a large dish. Holmes comes to Harrison, who alone does not congratulate him and asks to shake hands. The ring is missing. Sherlock gives it back to him and for the happiness of Phelps and Miss Harrison, he will keep silent on the brother's crime.