What caused the Great Fire of London? The Last Seal offers an explanation... September 1666: a struggle between two secret societies threatens to destroy London. Three hundred years previously the Praesidum defeated and incarcerated a demon beneath the city. Now the Liberati aim to release it and gain its power for themselvesAgents of the King are seeking four suspected foreign spies who are, in reality, disparate and unlikely heroes: GABRIEL, the sole remaining member of the Praesidum, crippled by his fear of failure; FREYA, a young thief orphaned by the Great Plague, driven by poverty and self-interest; TOBIAS, a cynical physician, obsessed by his desire for vengeance against the Liberati cavalier who killed his father, and finally and most vitally, BEN, a Westminster schoolboy, whose guilt over his parents' death threatens to destroy him. Yet these four must overcome their personal problems and work together if they are to foil the evil plans of the Liberati, protect the city and gain the means to defeat the demon. Thrown together by chance when Ben finds an ancient scroll revealing the location of arcane seals that bind the demon beneath London, the story launches into a battle between the Liberati and Praesidium, a battle which takes place within the Great Fire of London. Ultimately, Ben and his friends must confront and defeat both the demon and the evils of the Liberati to save their city and themselves.