A military translator is trying to figure out a traitor in the ranks of the Soviet army. Shy graduate student Dmitriy Neretin goes to the front to serve as a translator. After several weeks of intense battles, a lull begins. Battalion scouts advance to the front line and return with a prisoner - a German captain who mysteriously dies at night. Neretin finds out that the captured enemy was killed right in their location. Now Dmitriy will have to figure out a traitor among his associates who did not allow the prisoner to betray the secrets of the German army.