In the chaos of the Sierra Leone Civil War, a fisherman named Solomon is forced to work in the diamond fields while his family is torn apart. He discovers an extraordinary rough diamond and hides it just before being arrested. Meanwhile, Danny Archer, a Zimbabwean mercenary, learns about Solomon's diamond while in jail for smuggling. Upon their release, Danny devises a plan to take the diamond for himself. He seeks out American journalist Maddy Bowen, who is investigating conflict diamonds, in the hope that she can lead him to Solomon.

Archer, Solomon, and Maddy form an unlikely alliance. Archer promises Solomon help in finding his family in exchange for the hidden gem. Their journey to retrieve Solomon's diamond is fraught with danger as rebel forces and government troops battle for control of the country, and everyone seems to be after the precious stone for their own gain. Loyalties are tested, as each character grapples with their personal desires versus the atrocities they witness. Solomon yearns for his family's safety and to rescue his son from the clutches of the rebel army who has brainwashed him into becoming a child soldier, while Maddy wants to expose the blood diamond trade and Archer is initially motivated by profit but begins to show signs of a conscience.