Madrid, summer of 1938. In the middle of the Spanish Civil War, in the early morning of a certain day, the bullets of a sniper end the lives of two militiamen. Few hours later, Captain Matías and his men discover that the murderer was a boy who, determined to avenge the death of his Falangist brother, is still locked up in the house from which he shot. Some of Matías' teammates want to rush there and shoot him to death, but the captain wants to give him a chance. However, the boy refuses to surrender. He is only 15 years old. And he is not afraid of death. Because the only time one is not afraid of dying... is when one has barely lived at all. 15 is a story of the Spanish Civil War based on true events. But it is also a story about all wars and about the effect they have on those who fight in them.