Now, unmasking the killer becomes even more urgent. At a party celebrating Laura's return, McPherson arrests Laura for the murder of Diane Redfern. Upon questioning her, he is convinced that she is innocent and that she does not love Shelby. He goes to search Lydecker's apartment, where he becomes suspicious of a clock that is identical to the one in Laura's apartment. On closer examination, he finds it has a secret compartment. McPherson returns to Laura's apartment. Lydecker is there and notices a growing bond between Laura and the detective. Lydecker insults McPherson and is sent away by Laura, but pauses on the stairwell outside. McPherson examines Laura's clock and finds the shotgun that killed Diane. Laura is confronted with the truth: Lydecker is the murderer. McPherson locks Laura into her apartment, warning her to admit no one. After he leaves, Lydecker emerges from another room and attempts to kill Laura, saying that if he cannot have her, no one can. He is shot down by McPherson's sergeant, who had told McPherson that Lydecker had never left the building, causing McPherson and two other policeman to return to the apartment. Lydecker's last words are: "Goodbye, Laura. Goodbye, my love." Otto Preminger was looking for a theatrical project to direct and first became aware of Vera Caspary's story when her agent offered him the first draft of a play called "Ring Twice for Laura." Preminger liked the high-society setting and the unusual plot twist, but he felt the work needed a major revision and offered to rewrite it with its author. Caspary and he disagreed about the direction they should take it, and she opted to collaborate with writer George Sklar, instead. Marlene Dietrich expressed interest in portraying the title character, but without the attachment of Dietrich or another major star, Caspary was unable to find a producer willing to finance a national tour or a Broadway run, and she abandoned the project. Caspary eventually adapted the play for both a novel with the same title, and a sequel, which she titled simply "Laura," both of which eventually were purchased by 20th Century Fox for $30,000. George Sanders and Laird Cregar were announced as the leads. Interim studio head William Goetz, serving in that capacity while Darryl F. Zanuck was fulfilling his military duty, assigned Preminger the task of developing the books for the screen.