The young Daniel was guillotined for the murder of a policeman. Shortly after, his brother Jean has a terrible accident on a race track and shows irreversible brain damage. A medical team lead by Dr. Duval decide to attempt the first brain transplant on a human on Jean.

After the murder of Marianne Laforet, Jean attempts to escape by motorcycle, but is apprehended by the police.

Jean's trial starts. Meanwhile, a debate starts on the nature of brain transplant surgery - with the brain of another individual, can one maintain their own personality?