It's the turn of the 20th Century, and the skies above Alexandra Palace are alight with an array of aerial displays and showmen. And the crown jewel of the line-up? The fearless parachutists Betty and Lavinia, or as they are better known: The Butterfly and The Swan.

Betty, 18, is a plucky waitress who finds her calling after filling in for a missing parachutist. The thrill of flying is everything she's ever wanted, and more than that, it's an opportunity to make money in a world where it is near impossible for women to find any independence. Attractive and effervescent, she soon becomes a household name and crowd favourite alongside the more experienced Lavinia 'The Swan' Shawcross.

But whilst Lavinia knows nothing but this career, she dreads each jump more than anything. She's never really enjoyed launching herself out of the basket, experiencing only terror that these could be her last moments. But she is 32 years old and unmarried, so what options does she have?

Amidst the adoring crowds, there is a killer on the loose. He is determined to squash the suffragette movement and send a message about working women, and Lavinia and Betty are the ultimate prey.