In early 20th-century London, a series of mysterious events shakes the quiet lives of its inhabitants. Detective Charles Argyle, a former police officer with an innate talent for solving enigmas, becomes embroiled in the disappearance of a valuable family jewel belonging to the aristocratic Pembroke family. The jewel, known as "The Heart of the World," is more than just an adornment; it is said to hold a dark secret tied to a scandal from the past.
As Argyle explores the Pembroke mansion, he encounters an unusual mix of characters: the beautiful Lady Eleanor, trapped in an unhappy marriage; her jealous brother, Lord William, with a shadowy past; and the butler, who seems to know more than he lets on. Each of them has a motive and a secret, and as Argyle unravels the complexities of the family, he begins to question the loyalty of everyone.
The story unfolds amidst intrigues and betrayals, with unexpected twists at every turn. Argyle must utilize his wits and deductive skills to unravel the mystery before someone else falls victim to the dark legacy hidden in the family's past. Navigating through a labyrinth of lies and desires, the investigator realizes that sometimes, the most precious thing can be the truth itself.