London, 1923. Newly minted research assistant Saffron Everleigh is the first woman to hold the 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.

December 1899. After the death of her beloved grandmother, Cleopatra Fox moves into the luxury hotel owned by her estranged uncle in the hopes of putting hardship and loneliness behind her. But the poisoning of a guest on Christmas eve throws her new life, and the hotel, into chaos. Cleo quickly realizes no one can be trusted, not Scotland Yard and especially not the hotel’s charming assistant manager.

England, 1865: Newspaper columnist Lady Katherine Bascomb finds herself the subject of speculation when her latest article leads to an arrest in the murders plaguing London. The English believe women ought not to write about such vulgar things as crime, and a particularly attractive detective inspector is incensed that she's interfered with his investigation. To escape her sudden notoriety, Katherine heads to the country - only to witness a murder upon her arrival.

India Steele is desperate. Her father is dead, her fiancé took her inheritance, and no one will employ her, despite years working for her watchmaker father. Indeed, the other London watchmakers seem frightened of her. Alone, poor, and at the end of her tether, India takes employment with the only person who’ll accept her–an enigmatic and mysterious man from America. A man who possesses a strange watch that rejuvenates him when he’s ill.

As the city prepares to celebrate Queen Victoria's golden jubilee, Veronica Speedwell is marking a milestone of her own. After burying her spinster aunt, the orphaned Veronica is free to resume her world travels in pursuit of scientific inquiry - and the occasional romantic dalliance. As familiar with hunting butterflies as she is fending off admirers, Veronica wields her butterfly net and a hatpin with equal aplomb, and with her last connection to England gone, she intends to embark upon the journey of a lifetime.