Mission of the heart is a tragic love triangle between a teacher Linh and a young soldier Bach and an ex-soldier Trau. Although grown up in a rich family and graduated from abroad, Linh volunteers to teach in a school in the poor Talung area. Bach is a playboy who is sent to the army to train himself by his parents. When Bach’s sapper team comes to help Talung villagers clearing the landmines he finds out that Linh was his childhood neighbor. However, Linh has been pursued by a passionate Trau, an ex-solider, a savior of Talung villagers since a year ago. Trau has been traded collected landmines to make money to build road and bridges for the villagers. His illegal trading soon pushes him to meet with unexpected danger.