Geffroy, who spent two years in Iraq and Syria living among ISIS fighters, was captured by the Free Syrian Army whilst trying to flee Syria. When he was taken into French custody, he vowed to tell security services everything he knew about the group.
"From the moment I left ISIS until today, I made a commitment to say everything I knew about IS," he told the media.
Geffroy told French media that the son of the Clain brothers (the jihadis who claim responsibility for the Paris attacks) told him that 'adolescent kamikazes would be sent to Europe' by the Islamic State.
He also claimed the group had buried kalashnikovs in Toulouse, to be picked up at a later date by those intent on carrying out an attack.
Shockingly, Geffroy claims that the Brussels airport attack, which killed 32 people, was carried out " to prevent everyone being questioned".
He revealed that the intended target was actually a French nuclear power station.
"They had planned to go by car and blow up the cars," he told French media.
Geffroy claims the Clain brothers always leave their house in Raqqa wearing a burka, in order to prevent them being targeted in drone strikes.
When asked how France can trust him, now he is back in the country, Geffroy replies: "I think that when I made the anti-Western remarks, I was already in a process of IS regimentation, and that today I am opposed to it. said everything I knew about IS and involving my old friends, and that I'm ready to help France afterwards if I'm needed.
"I want to resume a normal life," he added.
Comment: ISIS jihadists are not only heartless fanatics, they also lack brains. Did they think that a car bomb at the entrance of a nuclear plant compound would make the whole nuclear plant blow like a nuke?