The Romanian Artillery is envied by the neighboring countries. A young foreign officer disguised as a painter crosses the border in order to steal the secrets of the newest cannon model. His plan is to seduce the granddaughter of a vigilant fort's guardian. He manages to do so but he is eventually caught by the guardian while trying to dismantle the cannon. A fight follows and the spy dies strangled, despite the girls' cries. In grief, she finally finds peace of mind while looking at the waving flag.