Twenty-five years have passed since Valeriy Starodumov worked as a dosimeter scout in September 1986. Valeriy worked at the epicenter of the explosion, the reactor's operation area, which was the most radioactive part of the site. The protagonist, a direct participant in the operation, went to the roof himself and brought people there after a failed attempt to clear the area with robots. At the government level, it was decided to assign soldiers and cadets of military schools to the task of cleaning the roofs. Unique pictures of the events of 1986 are widely used in the film. "Chernobyl.3828" is dedicated to people who saved the world from the radioactive contamination at the cost of their health and life.