What is the theme in At Bertram's Hotel by Agatha Christie?

Extreme adventure is a theme. Lady Bess Sedgwick likes doing things that today would be called extreme sports. Lady Sedgwick flies planes solo over the ocean, drives race cars, and enjoys doing just about anything a lady of her generation should not do, including breaking the law. Lady Bess Sedgwick's reputation is that of a woman who likes to create scandal. Lady Sedgwick has been married three times. The first marriage ended when Lady Sedgwick had an affair and ran away to be with her lover. This caused Lady Sedgwick to leave behind her only child, a daughter, who was then raised by her father until his death a few years later. The child then went to a family friend. Lady Bess Sedgwick never went out of her way to see or care for the child, deciding she was better off without a reckless mother such as her.