"The Secret of Chimneys" is a manga adaptation of Agatha Christie's classic mystery novel of the same name. The story revolves around a complex web of political intrigue, hidden treasures, and murder, set against the backdrop of the grand English estate known as Chimneys. The narrative begins with Anthony Cade, a young adventurer, who is entrusted with two tasks: delivering the memoirs of a deceased European count to a London publisher and returning a bundle of love letters to a prominent Englishwoman. These seemingly simple tasks quickly escalate into a dangerous mission as Cade becomes entangled in a high-stakes conspiracy involving international politics and a missing diamond known as the Koh-i-Noor.

The plot thickens when Cade arrives at Chimneys, the ancestral home of Lord Caterham, where a diplomatic gathering is taking place. Among the guests are Virginia Revel, a charming and resourceful woman; Superintendent Battle, a shrewd detective from Scotland Yard; and various foreign dignitaries with hidden agendas. The discovery of a murdered man in the house sets off a chain of events that uncovers long-buried secrets, including the true identity of the murdered man and the connection to the missing diamond. As the investigation progresses, Cade and Virginia find themselves working together to unravel the mystery, navigating through a series of red herrings, coded messages, and unexpected alliances.

Key characters include Anthony Cade, whose wit and resourcefulness make him a central figure in solving the mystery; Virginia Revel, whose intelligence and charm play a crucial role in uncovering the truth; and Superintendent Battle, whose methodical approach to the investigation provides a steady counterbalance to the more impulsive actions of the other characters. The story is driven by a combination of suspense, clever plot twists, and the interplay between the characters, culminating in a resolution that ties together the various threads of the mystery in a satisfying manner. The manga adaptation faithfully captures the essence of Christie's original work, presenting the intricate plot and rich character dynamics in a visually engaging format.