Larry Smith is a young bacteriologist on his way from New York to San Francisco to work under an eminent scientist in China. He stops along the way at the North house to deliver a scroll appointing socialite Mrs. North an honorary trustee of the hospital in recognition of her charity work. His visit interrupts the wedding of Mrs. North's spoiled daughter Diane to the stuffy Walter Corbett, and Diane, seizing the opportunity to dodge her nuptials, stows away in Larry's trailer, wearing nothing but her slip. On the road, Larry discovers that he has acquired a passenger and refuses to believe Diane's story that she is the daughter of the prominent North family. To placate him, Diane concocts a phony name and story and decides to win his heart while he determines to rid himself of her as soon as possible. As they venture across the country, however, the two fall in love and are married. Meanwhile, Mrs. North's offer of a reward for the return of her missing daughter triggers a nationwide search, and when Larry learns that he has married publicity hungry heiress Diane North, he throws her out and boards an airplane to fly to his boat in San Francisco. Diane follows him aboard, and the couple are reconciled as they voyage to China.