Lord John, brother of the Marquis of Haslemere, receives word from his friend, Carr Price, in New York, that the latter's dramatization of the detective story written by Lord John will not be purchased at all. This decision was brought about by Roger Odell, the millionaire friend of Julius Felborn, who has a strong animus toward Lord John, even though the latter does not know Odell. Odell arrives in London, but returns when he learns that Grace Callender is bound for New York. He books passage on the same steamer. Lord John learns of the hurried departure of Odell and determines to follow. On the boat Lord John hears Grace say to Odell in reply to his request to marry him, "No, Roger, do you suppose I could let you die like the others." Lord John's curiosity aroused, he opens his journal wherein he keeps notes to help him in his story writing, and sees that Grace had been successively engaged to Perry and Ned Callender-Graham, her cousins, but that in each instance just one week before the wedding each man was found dead in exactly the same place and each with a bunch of keys in his hand. No one could explain the cause of these deaths, and Grace vowed never to become engaged again and expose her affianced husband to the mysterious "curse." By the employment of an artifice, Lord John becomes acquainted with Odell, from whom he learns that the Marquis broke the heart of Odell's adopted sister. Maida, by canceling her presentation before the court. Lord John promises to atone for his brother's act, and before leaving the ship he makes an appointment with Odell to be in Felborn's private office within twenty-four hours. With the aid of Carr Price, Lord John is given permission by Yelverton of the police department to go through the records of the Callender-Graham case, and he learns that ten years ago Marian Callender, who was acquainted with Paola Tostini, a famous tenor, and who refused his offer of marriage, was given an inheritance on condition that she remain single and act as guardian over Grace. Tostini lost his voice and it was rumored that Marian shared her fortune with him, but her love for Grace was established when she urged her niece to accept Antonio, brother of Paola, notwithstanding that she would lose her income even in such an event. In an apartment occupied by a couple known as the Paulings, Lord John discovers a lock from which a needle containing poison projects when the knob is turned. The needle extends just far enough to touch the hand of the person opening the door. Lord John then goes to the country home of the Paulings, but the place is empty. The Lord, however, notices a picture of Marian Callender on the wall. A futile attempt is made by the Tostinis to steal the Egyptian mummy belonging to Maida Odell. The brothers are confederates of Dr. Rameses, whose present cult is hypnotism and Egyptian occult lore. Dr. Rameses has a twin sister who is the head of an organization known as The Gray Sisterhood, but in reality it is a branch of Dr. Rameses operations. Lord John writes a note to Grace Callender telling her to be at Felborn's office with her aunt in the morning. Marian Callender, the aunt, tells Dr. Rameses of the note and he informs her that she better go, as she cannot avert anything by staying away. He and the Tostinis follow her and stay outside the building. Lord John hides Roger Odell in the safe, and when Callender women appear he tells them that the double murder was carried out by two men and a woman, those interested in keeping Grace unmarried. Paola, a skilled chemist, compounding the poison. A woman was called upon to write the note decoying the brothers to a fiat on the pretext of learning a grave secret. Keys were enclosed for a midnight visit. The Callender-Grahams never learned the secret, being poisoned by the deadly needle only to hurry away and drop dead on the street. Marian Callender's hand resting on Grace's chair is so tightly clenched that her glove splits, revealing the poisoned ring which Dr. Rameses had given her. Lord John says, "I accuse the wife of Paola Tostini, still known as Miss Marian Callender." Marian attempts to get the ring to her lips. Grace struggles to prevent her and Roger bursts out of the safe in time to catch Grace, who is hurled aside. Marian eludes Lord John, and horrifies all by leaping out of the window to the pavement below. Lord John, Roger and Grace hurry out of the building, but find it is too late.