Isabella Chiswell, known to all as Izzy, is the daughter of Jasper Chiswell and Lady Patricia Fleetwood.¹ Izzy runs her father’s Parliamentary Office² and assists Robin in going undercover as Jasper’s goddaughter. While showing Robin around, Izzy explains that she’s “thrilled” Robin is there to help her father, saying that he’s “been under so much strain.” ³ Izzy tells Robin that she’s worked for her father for five years and is leaving soon to start a decorating company with a friend. She hopes that her brother, Raff, will end up taking over for her.⁴ 

Even when they display questionable behavior, Izzy is loyal to her family.  She is the only Chiswell who visited her brother, Raff, while he was in prison⁵ and, although she finds it sometimes difficult to work for her father (even breaking down crying at one point⁶), Izzy fiercely defends his secrets, never betraying him to Strike or Robin. The only member of the family who Izzy does not like is her stepmother, Kinvara, calling her “hysterical and attention seeking” ⁷ and believing her to be a “gold digger.” ⁸

We learn that Izzy has previously met Strike, as she is an old school friend of his ex-girlfriend, Charlotte.⁹ Izzy admits that she likes Strike saying that she “always quite fancied” him.¹⁰ While Izzy tends to be on the flirtatious side toward Strike, Robin ascertains that Izzy “isn’t his type.” ¹¹

Izzy is physically described as a tall, natural blond in her thirties¹² and, by Robin’s estimation, not beautiful.¹³

In Troubled Blood, Izzy proves to be an important contact for Robin in their attempt to interview Dennis Creed.¹⁴

^{1, 2: Lethal White, Chapter 12
3-5: Lethal White, Chapter 13
6: Lethal White, Chapter 27
7: Lethal White, Chapter 20
8: Lethal White, Chapters 27, 58
9: Lethal White, Chapter 12
10: Lethal White, Chapter 13
11: Lethal White, Chapter 64
12: Lethal White, Chapter 13
13: Lethal White, Chapter 64
14: Troubled Blood, Chapters 40 & 63}