In 1899, a secret society tried to use a young woman to bring an ancient evil into the world. Twenty years later they will return to finish the job. After the Great War, London is settling once more into the gentle routine of peacetime. The airships that once protected England's coast now ferry people back and forth across the Thames, the magically-inclined are free to return to their normal work, and those who seek treasures left behind by ancient civilizations are again free to explore. Dorothy Boone shunned a life of luxury to follow in her grandmother's footsteps by uncovering the mysteries of "the worlds that came before ours." When a package explodes upon delivery to Lady Boone's townhouse, she is drawn into an unlikely alliance with her nemesis, Trafalgar of Abyssinia, to find the culprit. They soon find themselves unraveling a plot that has left many of their allies dead and the rest in fear for their lives. A group of treasure hunters with a fiendish plot to take over England has begun eliminating its competition in order to fund an expedition to retrieve the last item they need for a summoning that will bring an ancient evil into our world. With no one else to trust, Trafalgar and Boone must put aside their differences and forge a partnership to stop their mutual enemy. If they fail, a world that still bears the scars of the Great War will be once again thrown into turmoil. Welcome to the world of Trafalgar and Boone, a world where airships battled in a Great War that was fought by soldiers who utilized magic and summoned monsters to do their bidding, a world that they must defend by working together to stop an evil far greater than either of them could ever have imagined.

Dorothy Boone's attempt to help a friend leads her to an encounter with a deadly new rival. Trafalgar and Boone have been working together for a year, taking small commissions in order to learn how to work together. When a friend and colleague is committed to an asylum following a disastrous mission in the Mediterranean, Dorothy takes it upon herself to uncover the truth. What she finds is that her friend was close to the discovery of a lifetime: the remnants of a prehistoric civilization who might have been wiped out by the Biblical Flood. Trafalgar agrees to accompany her on an expedition to finish what her friend began, and soon they run afoul of a powerful enemy: Emmeline Potter, called Virago, is a treasure hunter who is also adept at magic and seeks riches to help fund a violent uprising. Dorothy and Trafalgar must race to defeat their unscrupulous opponent if they hope to preserve the site for future generations, but they soon discover Virago may be the least of their worries. The secrets of the past have ways of remaining hidden, and trying to uncover them may cost Dorothy her life.

Miss Trafalgar and Dorothy Boone have grown comfortable in their partnership. The rough edges on the society they formed with their fellow adventurers have begun to smoothe, opening the doors for a new era of cooperation among one-time enemies. When Trafalgar receives an Egyptian statue, a gift from her former assistant, she asks Dorothy to determine its authenticity. What Dorothy uncovers throws both of them, along with the rest of the Mnemosyne Society, into chaos. With lives at risk and the future at stake, Trafalgar leads a group of reluctant allies from London to Egypt to stop an unspeakable power from falling into the wrong hands. Meanwhile, Beatrice Sek continues her quest to discover her true origins. Armed only with the knowledge that she is one of four "Elementals," she spends her spare time searching for anyone who may know where she came from. She receives unexpected assistance from a former foe, a powerful enemy who promises to help her find answers. The offer is too good to refuse, no matter who it's coming from, but Beatrice may soon find herself forced to choose between revelation and surrendering her soul.

Dorothy Boone, still blaming herself for a devastating loss on their last adventure, and Miss Trafalgar are offered a new mission from the Royal Geographical Society: an expedition to find the source of a mythical river has gone missing in the Amazon rainforest, and their patrons want them found. It seems like the perfect low-threat endeavor to get the duo back to normalcy, so Dorothy and Trafalgar accept. Accompanied by Cora Hyde, who is also recovering from a loss, the duo sets out for the jungle. Their safe undertaking soon turns perilous when they run afoul of a previously unknown tribe known as the Burnt Empire. Dorothy and Trafalgar are separated in the scuffle and taken in by two groups with similar goals but differing tactics. The groups only agree on one point: the very existence of the Burnt Empire could lead to untold destruction.

Trafalgar and Boone have faced danger from all around the globe, but their greatest threat may be lurking very close to home. A quiet period of rest and recuperation between adventures is interrupted by the arrival of two constables on the front steps of Dorothy Boone's townhouse. A woman was seen dumping a dead body outside a hospital near Threadneedle Street, and Dorothy matches the description given by witnesses. Dorothy manages to avoid arrest and takes it upon herself to investigate the crime, enlisting other members of the Mnemosyne Society to help. She quickly discovers the Forty Elephants, a gang of all-female thieves, has been revived by a woman named Maud Keaton and makes it her mission to bring them down. But Maud Keaton is very aware of Lady Boone and Miss Trafalgar. She knows all about Dorothy's vault of mystical objects and will go to any lengths to gain access to it. Lines are quickly drawn in the sand, with the Elephants on one side and the Mnemosyne Society on the other. Faced with an enemy who is her match in both cunning and intellect, Dorothy quickly discovers that victory may be impossible, or come with a cost she's unwilling to pay.

Trafalgar and Lady Dorothy Boone, still shattered by the consequences of their last mission, have decided to heed a warning from the future and put an end to the widespread use of magic. While Dorothy sits vigil for someone she loves, Trafalgar accepts the invitation from a fellow Society member to investigate an ancient queen's burial site. A simple mission quickly turns sour, and Dorothy finds herself racing to save not only her friend and partner, but the whole of London. While the Society is stronger than ever, Dorothy herself is alone without her closest allies and advisors. Faced with the choice of a horrible loss and a potentially catastrophic future, Dorothy makes a decision which could change the world forever... and cost her the very thing she hopes to save.

When we last visited our intrepid heroes... The partnership between DOROTHY BOONE and MISS TRAFALGAR had come to an ignominious end. A protective curse on an ancient queen’s gravesite felled not only Trafalgar but infected all of London with a fatal virus, forcing Dorothy to take extreme measures to prevent a catastrophe. Her actions stopped the illness, but the people of London were imbued with new and dangerous magical abilities. To put things right, BEATRICE SEK and the other three elementals united at the Tower of London to create the fifth void. Their plan worked, and magic was effectively dampened, but at a tremendous cost. Beatrice has apparently lost her life, and Dorothy’s rash actions during the crisis led to a rift with Trafalgar which eventually led to an agreement to part ways. The world marches on. The MNEMOSYNE SOCIETY continues to grow and thrive, with the former members of the Forty Elephants proving themselves worthy new additions to the ranks. Scotland Yard has come to respect the contributions of the group and often consults them in situations that have a supernatural bent. It has been seven years since Dorothy Boone and Miss Trafalgar were alone in a room together, but that is soon to change.