Solomon Vandy and his family live in a small village in Sierra Leone, which is attacked by the Revolutionary United Front. Many people are killed, Vandy's wife and daughter can escape, but his son is found by the rebels and made a boy soldier. Vandy himself is caught and has to work in the diamond fields. There he finds a diamond weighing about 100 carat and he decides to hide this stone near the field.

Danny Archer is a white South African mercenary, who smuggles diamonds from Sierra Leone to Liberia. He is working for Colonel Coetzee. He is arrested at the border and put into prison where he meets Vandy, who tells him about his diamond. For a part of the stone Archer promises to help Vandy finding his family.
Together with the American journalist Maddy Bowen they find Vandy's wife and daughter in a camp for refugees. Archer gives Bowen information about the trade with blood diamonds in exchange for her help.
Finally Archer and Vandy reach the diamond field with the hiding place of Vandy's diamond. The field is defended by rebels, among them Vandy's son. Archer is able to organize an air attack by government troops. Vandy kills an officer and two soldiers, who want him to give away his diamond, as he fears they would kill him if he obeys.
Vandy and Archer free Vandy's son and find the diamond, but Archer is wounded. Vandy tries to save him and take him to the waiting plane, but Archer is too weak and dies. But short before his death he gives back the diamond he is carrying.

Vandy and his son escape. Vandy goes to London to help Maddy Bowen finding out about the backers of the diamond trade. Finally he becomes an activist against the trade and the smuggling and holds a speech in front of many politicians.