Laughter Epidemic is an old Vietnamese film directed by Do Minh Tuan that tells the story of a hydroelectric power plant that is about to be built in the countryside. When the general director came here, he said that "the valley of pain will turn into a field of happiness". Since then, there have been rumors that the CEO lost his ring while swinging his hand to give a speech. Many funny situations take place after that. The workers are mobilized to give up all their jobs to find a ring for the general manager, subordinates have to buy a new ring to return it to their superior, even though it turns out the ring wasn't actually lost.