Sally Elliott and Humphrey Briggs want to get married and buy a house, but cannot afford it even with their combined salaries from the Maritime Steamship Company, where Sally is a switchboard operator, and Humphrey is a file clerk. After the cargo supervisor is fired, Sally encourages the timid Humphrey to apply for the job. Unknown to Sally and Humphrey, Harvey Simpson, the head of the company, is smuggling diamonds and wants to replace the former supervisor with a stupid man, like the unassuming Humphrey. On the strength of his new position, Humphrey puts a down payment on a house. At the office, Sally's friend, Jane Bixby, a Fuller Brush saleswoman, stops by to demonstrate the cosmetics she is selling. While trying the cosmetics, Sally manages to blow up the switchboard and is fired. Jane then convinces her to apply for a job as a Fuller Brush Girl. Sally needs good references, however, and because she is sure that Simpson will not give her one, she decides to prove her sales abilities by taking over Jane's route for a few days. Meanwhile, Simpson's wealthy wife Claire smells cosmetics on his clothes and accuses him of having an affair. Consequently, when Humphrey approaches him about Sally, Simpson makes a deal to give Sally a good reference if she will tell his wife what happened. On her route, Sally learns that selling cosmetics is not easy. At the first house, the housewife sells her a magazine subscription. At the next, she is mistaken for the baby sitter. At the third, Sally gives home permanents to a group of women playing cards and mistakenly applies chemicals from a boy's chemistry set that cause all of their hair to fall out. Then Humphrey tracks Sally down and sends her to talk to Claire. In the meantime, Simpson, who has learned that Claire has started proceedings to remove him from the company, instructs burlesque dancer Ruby Rawlings to pretend to be Sally. When Sally arrives at the Simpsons, Ruby knocks her unconscious and places a gun in her hand. Humphrey arrives shortly afterward and discovers Claire's slain body. He calls the police, then discovers the unconscious Sally. Sally is sure that she must have killed Claire, although she does not remember doing so. Hoping to straighten things out, Humphrey and Sally go to Simpson's office, where Humphrey finds Simpson's body. Outside, Sally sees a poster advertising Ruby's show and recognizes her assailant. At the burlesque theater, Sally pretends to be a dancer in order to get backstage. She then sneaks into Ruby's dressing room and overhears her arrange to meet a man named Rocky Mitchell at a ship. Sally ties Ruby up and telephones the police, but Rocky, who has just arrived, overhears the call and chases Sally around the theater, trying to kill her. To escape her pursuer, Sally dashes onto the stage and starts to perform. Afterward, she leaps off the stage into the audience and, together with Humphrey, runs from the theater. They are seen by Watkins, a member of the smuggling gang, who pretends to be taking them to the police. Instead he takes them to the Clair S. , the company's ship. At the theater, Ruby tells the police that Watkins, Rocky and Simpson were smuggling diamonds on the Claire S. When Ruby pretended to be Sally, Claire grew suspicious, and Watkins killed her. After the murder, Simpson was killed to stop him from talking to the police. The police then hurry to the docks. By various means, Sally and Humphrey manage to evade the crooks until the police ship arrives.