A journalist wrongly accused of murder enlists the help of a femme fatale to track down the real killer.

Loïc, a chestnut seller, has a mistress who wants a baby. Not daring to admit to her that he had the mumps late in life, he finds other excuses. Until the day he meets Claire, an old girlfriend, who has a little boy. Loïc finds the resemblance between the little boy and himself enormous and is convinced that he is his father...