Tank commander Sergeant Tessen does not believe that his crew can become a successful collective and requests his transfer, but he finally withdraws his request due to a young boy to whom he carelessly promised a tank model. However, this would first have to be made by the crew . New difficulties arise, even though everyone agrees to keep the soldier's word of honor. The spell is only broken when the tank gets into a dangerous situation during an underwater journey and the four of them have to prove themselves together.