Ace Carroway and the Handsome Devil (The Adventures of Ace Carroway) by Guy Worthey

It’s 1921 and the world mourns the disappearance of aviatrix Cecilia “Ace” Carroway, lost during a ’round-the-world attempt. Barely, Ace survives what she knows was an assassination masterminded by underworld kingpin Darko Dor. In secret, she gathers her five wartime comrades and opens a detective agency, intending to hunt Dor and his ilk.