After his brother Luc's suspicious death in Tangier, Marseille port worker Jean Moreau uncovers a cryptic clue: the "Fourth Key," a missing element tied to a secretive post-Algerian War French intelligence operation. As Jean follows a trail of coded manuscripts, hidden safes, and dangerous allies, he is drawn into a deadly web of mercenaries, corrupt officials, and long-buried secrets.With the help of Luc's ex-girlfriend Elise and historian Dr. Dupré, Jean navigates secret passages, shadowy docks, and betrayals that push him to the edge. The final confrontation exposes the full truth behind the Fourth Key and forces Jean to face the personal cost of uncovering a decades-old conspiracy.Suspenseful, realistic, and fast-paced, The Fourth Key is a story of loyalty, betrayal, and the dangerous weight of secrets that refuse to stay buried.