A man frozen for 65 years is found in the ice of the North Pole by a scientific polar expedition. While he is brought back to life by professor Edouard Lauriebat (Michael Lonsdale), the man is identified as Paul Fournier, who was exploring the pole in 1905 and is now, thanks to hibernation, a 90 years old young man. Edmée de Tartas (Claude Gensac), born Fournier, is identified as the granddaughter of Paul and convinces her husband, Hubert Barrère de Tartas (Louis de Funès), that Paul must be given back to his family, while the government wishes to treat Paul as a research subject. After a kidnapping and a pursuit, the authorities reluctantly agree, but impose, for the sake of Paul's mental health, that his environment be the same as in 1905. As Paul thinks Edmée is his mother, Hubert must play the role of a man courting Edmée and Didier (Olivier de Funès), the son of Edmée and Hubert plays the role of a student living with the family. First under control, the situation gradually deteriorates especially when Paul's actions become a threat to Hubert's plan to marry his son to the daughter of Crepin-Jaujard, one of his business partners.