1920s London isn’t the ideal place for a brilliant woman with lofty ambitions, but research assistant Saffron Everleigh is determined to beat the odds in a male-dominated field at the University College of London. She embarks on her first research study alongside the insufferably charming Dr. Michael Lee, traveling the countryside with him in response to reports of poisonings. But when Detective Inspector Green is given a case with a set of unusual clues, he asks for her assistance.

The victims, all women, received bouquets filled with poisonous flowers. Digging deeper, Saffron discovers that the bouquets may be more than just unpleasant flowers—there may be a hidden message within them, revealed through the use of the old Victorian practice of floriography. And it's a dire message indeed, as each woman who received the flowers has turned up dead.

Alongside Dr. Lee and her best friend, Elizabeth, Saffron trails a group of suspects through a dark jazz club, a lavish country estate, and a glittering theatre, delving deeper into a part of society she thought she’d left behind forever.

Will Saffron be able to catch the killer before they send their next bouquet, or will she find herself with fatal flowers of her own?