Private investigator Harry Dobbs argues with Doris, his jealous girl friend, but just as they are about to make up, he receives a telephone call from Miss Dolan, a prospective client. Despite hearing Doris shouting in the background about “another woman,” Miss Dolan hires Harry, agrees to his $500 retainer fee, and asks him to meet her at the Blue Danube Supper Club. Arriving there, Harry meets a beautiful, classy woman who wants him to follow a man named Rick. Miss Dolan pays the detective a $2,000 retainer, describes the quarry, and informs Harry that Rick will be at the club at 9:00 p.m. She warns that Rick appears charming but is very dangerous. After telling Harry the name of the expensive hotel where he can contact her, Miss Dolan leaves without giving him Rick’s last name. A man fitting Rick’s description arrives later with a woman. They kiss on the dance floor, and when they leave, Harry Dobbs follows and jots down the license plate number. After stopping at a neighborhood grocery store, Rick takes the woman home to a middle-class house, where three children are waiting, and goes inside. Harry returns to the grocer and learns the man’s name is Mr. King. The next day he watches as the woman, the older family nanny, and the three kids walk Mr. King to his car. Harry follows him to an office building downtown and sees Fredrick King’s name listed on a lobby board under Wickman Investment Company. At the Blue Danube, Harry tells Miss Dolan about Rick’s other identity as a married man. He offers to call off the surveillance and return half the retainer, but Miss Dolan insists he keep going. Another woman, Stella Wynkowski, eyes Harry as she walks past him. When Miss Dolan leaves, he follows her to a nightclub, where she croons torch songs with the band. The next morning, Harry follows King to the airport and buys a ticket on King’s flight. At the destination, Harry watches King put his briefcase in a locker and go into a bathroom with a large bag. When King emerges, he is wearing a cowboy hat and Western clothes. Harry’s cab follows King’s cab, as Stella Wynkowski follows them in a car. King is dropped off at a garage and drives away in a pickup truck, which Harry follows to the Crooked River Ranch. He takes photographs of King being greeted by a woman and child. Nearby, Stella watches Harry. She follows him to the Sunrise Motel in the nearby town of Culver, and checks in separately. Harry telephones Miss Dolan and describes the ranch and Rick’s second family. Next, Harry telephones his girl friend, Doris, but she screams at him and hangs up. Going for a walk, Harry notices Stella half dressed through her window. The next morning, Harry buys a used car for $250 and drives to the ranch. Using the ploy of being lost, he engages the woman of the house, Ellen McGraw, and offers to pay to use her telephone. She offers Harry a cup of coffee. Feigning a telephone conversation using the name Harry Johnson, Harry witnesses Ellen in a tender moment with Art, one of the ranch hands. As Mr. King, now James “Jim” McGraw, enters the house, Harry greets him warmly and thanks him for the use of his telephone. Later, Harry follows King/McGraw to the nearby Rock Creek Tavern, where McGraw makes a telephone call to a woman. Stella sits nearby, drinking a beer. McGraw talks with Cal, the bartender, who asks how long he will be around before returning to his “other spread.” Later, on the road, Harry's car breaks down. As Stella stops behind him, Harry recognizes her from the Sunrise Motel and asks her to drive him there. Later, Stella telephones her client, Doris, to inform her that Harry is actually working on a case and not cheating, but Doris becomes jealous and fires her. That night, Miss Dolan telephones Harry to inform him she has relocated to the Devonshire Hotel under another name because Rick has threatened her. Harry flies home in the morning, notices Stella on the airplane, and sits across the row from her. He asks if she is working for King/McGraw. She criticizes his detective skills because he got too close to his quarry, and he calls her careless at her job for picking him up on the road. Noticing Stella is reading a love manual, Harry discusses the topic. Stella gets him to talk about his girl friend, and Harry says he still loves Doris despite her jealousy. As they part company at the airport, Stella gives Harry her name, but not the name of her client. Harry visits Miss Dolan at the Devonshire to deliver his report. She begins to seduce Harry, but a knock on the door frightens her. It is the bellhop with her dry-cleaning. Harry gets another room on the same floor of the hotel, and the bellhop reports that information to an older man named Harvey. Meanwhile, Corrine Dart, head of the detective agency where Stella works, fires her because the client, Doris, does not like her. The next morning, Harry cannot find Miss Dolan in her room. Harry drives to Mrs. King’s home, identifies himself as Mr. King’s old friend, and asks if the names James McGraw or Miss Dolan mean anything to her, because he wants to get in touch. When Harry returns to his car, Stella is waiting. They drive to the Blue Danube, where she suggests he needs a business partner with a woman’s intuition. Stella agrees to fly back to the McGraw ranch for Harry, and they kiss. As they leave the club, Harvey, the older man at the Devonshire Hotel, is watching. Back at the hotel, Harry telephones Stella and tells her to be careful. When Stella hangs up, her former boyfriend Marty telephones and asks if there is someone else. Stella hangs up on him. Pounding awakens Harry, and when he opens the door, Harvey hits him, but Harry pulls a gun and chases him off. Meanwhile, Stella drives to the ranch and asks to use the telephone. Feigning a telephone call, she watches Ellen kissing Art, the ranch hand. McGraw walks in, catches them, and berates Ellen after Art hurries away. Stella returns to her car. Harry revisits Mrs. King, but she becomes suspicious, asks if he is an enemy of her husband, and drives Harry away, calling him “the Devil.” At the Rock Creek Tavern, the half-drunk McGraw sits next to Stella and talks about the exhilaration of living life dangerously. When she drops hints that she knows his “King” identity, McGraw becomes threatening. However, Art enters the bar and confronts McGraw about ruining Ellen’s life. As the two men fight, Stella slips away. Harry returns to the Blue Danube and sees Miss Dolan leaving with Rick, who resembles the Fredrick King he has been following, but is not the same man. Harry discovers that Rick’s chauffeur and bodyguard is Harvey, the man who attacked him. Stella Wynkowski returns to the ranch and tells Ellen and her daughter that she has come to take them away. Ellen packs and lets Stella drive her and her daughter to the airport. Harry Dobbs follows Rick home, hits Harvey as he opens the front door, and knocks Rick out a window. Miss Dolan is sitting in bed, waiting for Rick, but Harry makes her leave with him. Now back in town, Stella sees Harry and Miss Dolan and follows them to the train station. Miss Dolan, who finally reveals that her first name is Gwendolyn, asks Harry if he loves her, but Harry reveals that he loves someone else. He puts her on the train. Meanwhile, Fredrick King returns to Mrs. King. Stella returns home, and her ex-boyfriend, Marty, forces his way in, insisting he wants her back. Stella chases him out with a gun. Harry is already waiting inside Stella’s apartment. He reveals that he was following the wrong man all along. As Harry confesses his love, they realize they have both solved the other’s case. They make love.