Isabella 'Izzy' Stone is an agent with the American Secret Service.
When we first meet her she is the lead agent in charge of the protection detail for the President of the United States and as such, she bears an incredible responsibility. Normally someone in such a job would not qualify for membership in this compendium but considering the things that happen to her on a Presidential road trip and afterwards, she more than has justification for being here.
She is described as standing 5'9", possessing a "shapely body [which] still radiated the ramrod posture and athleticism West Point had instilled in her years before". That fairly short but still interesting Army career would get her posted as a military attache to the Paris embassy, a stint that will be a factor in later events as well for both of the initial adventures we have of Stone take place in and around Paris, a city that she loved and knew fairly well from having lived there for several years as a child.
Stone is dedicated to her work, a fact she shows all too dramatically and painfully (for her) in an opening chapter of the first adventure. This is attested to with "she'd seen violence of the worst kind over the years, had been on the receiving end of it more than once, and had employed deadly force protecting the president".
"Izzy was fluent in French, Spanish, Hebrew, Arabic and Russian. Languages came to her as naturally as breathing - an aptitude inherited from her dad, a renowned UCLA linguistics professor." This talent will come in very useful in the adventures that ensue.
She is large unattached in her personal life; in the first adventure she is said to have an on-and-off relationship with a Greg Neal, a "wonky" fellow who is a member of a Washington think tank, but considering the demands placed on her by her employment, anything more serious is not likely.