When Trin, the leader of a criminal group called the Messengers, gets wind of a plot to eradicate crime in an alternate Victorian London, she enlists the help of two fellow crooks, Marion and Red. Marion is a shapeshifter who loves nothing more than chaos, manipulation, and a lacy pink dress. Red is the transgender son of a noble family, living a double life as the leader of the Scarlettes, the largest and cruelest gang in London. Despite mutual animosity, impossible-seeming obstacles, and an unknown force meddling in their affairs, the three uncover a secret that could grant them power beyond their wildest dreams. Together, they attempt a daring heist to take it for themselves, and in the process realize that everything they thought they knew about the world they live in, and about one another, was wrong.