富顿教授(加里·格兰特 Cary Grant 饰)是一位科学家,正在研究一种能够让人返老还童的神奇药物。某一天,富顿用来试验药物的黑猩猩从笼子里逃了出来,在实验室里“大闹天宫”,没想到竟然在误打误撞之下将富顿一直想要研制但始终没有成功的神药给捣鼓了出来。 对此一无所知的富顿在偶然间喝下了这种药物,很快,药效便发挥了作用,富顿一反常态,言行举止俨然一幅二十岁小伙子的模样。秘书路易斯(玛丽莲·梦露 Marilyn Monroe 饰)前来拜访富顿教授,没想到却被他邀请去游泳、溜冰。之后,富顿的妻子爱德华(金格尔·罗杰斯 Ginger Rogers 饰)亦误食了药物,一连串让人忍俊不禁的趣事就此展开。Barnaby Fulton is a research chemist working on a fountain of youth pill for a chemical company. While trying a sample dose on himself, he accidentally gets a dose of a mixture added to the water cooler and believes his potion is what is working. The mixture temporarily causes him to feel and act like a teenager, including correcting his vision. When his wife gets a dose that is even larger, she regresses even further into her childhood. When an old boyfriend meets her in this state, he believes that her never wanting to see him again means a divorce and a chance for him.