Joëlle, a simple and energetic young woman, works as a hairdresser for Mrs. Delbarre. When Professor Thibaud, a great bone specialist, asks her to donate her bone marrow for a transplant, on the condition that she does not seek to know the recipient, she accepts without hesitation. But the temptation is too strong and she investigates in order to discover the person who benefited from her generous gesture. It is a handsome young man with whom she immediately falls in love.