Simon Gautier, who was studying art history in Rome, was last heard alerting emergency services in a call in which he said he had suffered a fall while trekking a remote area near Naples and had broken both legs.
Suspects planned to use corrosive acid to dissolve dismembered corpse of 23-year-old female victim, as depicted on TV show.
The Green activist, who was once known as 'Dany the Red', was expelled from France after leading student uprising in May 1968.
Headteacher reportedly felt long skirt 'conspicuously' showed religious affiliation, which is banned in French schools under strict secular laws.
An audacious North Korean kidnap plot is foiled at Paris Charles de Gaulle airport as 'Asian men' attempted to bundle student onto plane.
Mother sues couple who saw her drunk son and who 'laughed at him, filmed him with a smartphone and let him leave' rather than help him.