Ninth grade pupils of one of the Moscow schools undergo the summer internship at a large haulage company. Having quickly made themselves familiar with uncomplicated repairman job the guys choose in their friendly team a suppler - and everyone finds something useful in the practice. Only Sergei Krasheninnikov (Krosh) with their humanitarian skills and a complete lack of interest in technology, clearly, stands out from friendly staff. But the emergency happens: first, a new shock absorber disappears from the storehouse, then - a car. And the observant Krosh assumes the functions of the detective.