1904. Three years since the death of Queen Victoria and the ascension of her son, Edward VII to the throne. In that time, the decline of the British Empire has accelerated, the economy has stuttered, Scott has gone to the South Pole, and Liberal politician, Felix Grey has been parachuted into Number Ten on the crest of a populist wave. The third youngest Prime Minister in history and the son of a Suffragette, Felix is modern and progressive, but also inexperienced, self-deprecating and doubtful.
Having taken on the Conservative old guard in the House of Commons, Felix has found his policies continually blocked and his time in power dogged by his inability to affect any real change. However, when a member of the House of Lords is abducted from the East India Club, and a mysterious card is discovered, Felix begins to feel a sense of purpose again. Against his better judgement, and that of his loyal steward, Humphrey, Felix begins to dig into the card and the missing Lord, desperate to be of service to the people he represents. A trip to Corpus Christi, to consult bumbling Texan professor, Abe Woodruff, only cements Felix's infatuation with the mystery, and he begins to neglect his role as Prime Minister in favour of traversing the city, surreptitiously chasing clues and following up on leads.
With public approval disappearing under a spate of fatal factory disasters, and the emergence of the German and American economies making the front pages, Felix's premiership is suddenly under attack from all sides. Lost and despairing for his career, Felix accidentally stumbles upon a secret passage in his study, running half a kilometre underground to a tired and hidden office in Old Pye Street. On the walls are pictures of notable past Prime Ministers, and a plague, with the inscription; Old Pye Street. Built for service, but reserved for only the most curious, benevolent and adventurous.
When another Lord is abducted, Felix begins to escalate his investigation, determined to uncover the truth. A fire at one of Fleet Street's oldest printers brings young, homeless, apprentice, Alfred into Felix's life. Although illiterate, Alfred can fix anything, and Felix allows him to stay at Old Pye Street, rather than see him abandoned on the streets. Alfred uses his talents to bring the room's old facilities back to life, and it's not long before the pair form a trusted bond.
Further trips to the Carlton Club, the Masons, the Tower of London, the Docklands, the Matchmakers of Bryant and May, and the House of Commons begins to reveal a connection between the abducted Lords and the factory disasters. Realising that it has all been orchestrated to create mass discontent in the run-up to the state opening of Parliament, Felix is suddenly against the clock to understand why anyone would want to create such widespread chaos. With numerous links back to fellow MPs, businesses in Yorkshire, and a period synonymous with British history, Felix has to fight off his enemies, unmask the perpetrators, find the missing Lords, keep Alfred safe, and solve the case, while protecting his identity and preserving his position as the British Prime Minister.