Captain Harry Cathcart has fallen on ill luck and is earning a living as a private detective. He is hired to break up the engagement of Lady Rose Summer and her fiance Sir Geoffrey Blandon. After a scandalous break-up, Rose attends a weekend party to revive what is left of her matrimonial prospects. Instead of romance and marriage she finds a murder case. She and Captain Carthcart join forces to solve the crime.

Lady Rose Summer, the daughter of an earl, and her maid Daisy defy the conventions and join the working world. In her job at a bank, Rose discovers evidence of possible blackmail in a murder case. With Daisy and her detective friend Captain Harry Cathcart, she undertakes an investigation.

To avoid being sent off to India, Rose pretends to be engaged to Captain Harry Cathcart. When a new friend from the country, Dolly Tremaine, is found is found floating in the river, Captain Cathcard is called to investigate.

Lady Rose Summer is suspected of murdering out of jealousy a beautiful client of detective Captain Cathcard.