1916. As thousands of Brits are fighting on the Front Line, a new breed of fiercely independent and fiery-spirited women emerge to hold the Home Front together. Among this raucous group of munitionettes, or 'canaries', is Florrie Duncan whose birthday celebrations are tragically cut short when a brutal explosion kills all but one of the party. Unconvinced it's the work of a German spy as Scotland Yard surmise, Detective Inspector Harvey Marmion and Sergeant Joe Keedy believe something more complex and sinister is at play. Suspicion is rife and as the pair begin to piece together the lives of the women, they unearth a tension simmering between many of the locals and the canaries. Marmion and Keedy must work fast to uncover the murderer before more canaries are turned to dust ...