High-profile heiress Diane North (Wendy Barrie) stows away in the trailer of a bacteriologist Dr. Lawrence "Larry" Smith (Gene Raymond) to escape from her own wedding. Larry has to drive cross country to San Francisco to catch a ship to China, where he will work with an eminent expert on a cure for a serious disease. When he discovers his stowaway, Diane tells him she is poverty-stricken Maggie "Jonesy" Jones, making her way to a slightly less poor uncle. Larry tries to get rid of his passenger at every opportunity, but she falls in love and uses every wile to stay with him.