London, 1923. Newly minted research assistant Saffron Everleigh is the first woman to hold this position at University College of London. When she attends a dinner party for the school, she expects to engage in conversations about the university's large expedition to the Amazon. What she doesn’t expect is for Mrs. Henry, one of the professors’ wives to drop to the floor, poisoned by an unknown toxin.

Dr. Maxwell, Saffron’s mentor, is the main suspect and evidence quickly mounts. Joined by enigmatic fellow researcher Alexander Ashton, Saffron uses her knowledge of botany as she explores steamy greenhouses, dark gardens, and deadly poisons to clear Maxwell's name. Will she be able to uncover the truth or will her investigation land her on the murderer’s list?